diff --git a/.evergreen/build_example_projects.sh b/.evergreen/build_example_projects.sh
index 33bf5fbf4e..d75363a09e 100755
--- a/.evergreen/build_example_projects.sh
+++ b/.evergreen/build_example_projects.sh
@@ -15,17 +15,20 @@ for project in bsoncxx mongocxx; do
     cd $project
 
     if ! ( cd cmake/$DIR && ./build.sh >|output.txt 2>&1); then
+        echo "Example $project/cmake/$DIR failed" 1>&2
         cat cmake/$DIR/output.txt 1>&2
         exit 1
     fi
 
     if ! ( cd cmake-deprecated/$DIR && ./build.sh >|output.txt 2>&1); then
+        echo "Example $project/cmake-deprecated/$DIR failed" 1>&2
         cat cmake-deprecated/$DIR/output.txt 1>&2
         exit 1
     fi
 
     if [[ ! ( "$OSTYPE" =~ cygwin ) ]]; then
         if ! ( cd pkg-config/$DIR && ./build.sh >|output.txt 2>&1); then
+            echo "Example $project/pkg-config/$DIR failed" 1>&2
             cat pkg-config/$DIR/output.txt 1>&2
             exit 1
         fi
diff --git a/.ycm_extra_conf.py b/.ycm_extra_conf.py
index 708d7c088a..71f2b56a72 100644
--- a/.ycm_extra_conf.py
+++ b/.ycm_extra_conf.py
@@ -45,7 +45,6 @@
     '-x', 'c++',
     '-Isrc',
     '-Ibuild/src',
-    '-Ibuild/src/bsoncxx/third_party/EP_mnmlstc_core-prefix/src/EP_mnmlstc_core/include',
     '-Isrc/third_party/catch/include',
     '-I/usr/local/include/libmongoc-1.0',
     '-I/usr/local/include/libbson-1.0',
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 942ad21f71..91fe4fcaa8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 - Do not build tests as part of `all` target. Configure with `BUILD_TESTING=ON` to build tests.
+- Bump minimum required CMake version to 3.15 to support the FetchContent module and for consistency with the C Driver.
+- Improve handling of downloaded (non-system) mnmlstc/core as the polyfill library.
+  - Use `FetchContent` instead of `ExternalProject` to download and build the library.
+  - Do not patch include directives in mnmlstc/core headers.
 
 ### Fixed
 - Explicitly document that throwing an exception from an APM callback is undefined behavior.
+- Do not prematurely install mnmlstc/core headers during the CMake build step.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d74ba2d64f..d160c8abbd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-cmake_minimum_required(VERSION 3.2 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.15)
 
 if(POLICY CMP0025)
   cmake_policy(SET CMP0025 NEW)
@@ -458,4 +458,3 @@ endif ()
 if (CMAKE_GENERATOR_TOOLSET)
    message (STATUS "\tinstance: ${CMAKE_GENERATOR_TOOLSET}")
 endif ()
-
diff --git a/cmake/BsoncxxUtil.cmake b/cmake/BsoncxxUtil.cmake
index 5d1f077b37..ec2b596d5d 100644
--- a/cmake/BsoncxxUtil.cmake
+++ b/cmake/BsoncxxUtil.cmake
@@ -29,21 +29,15 @@ function(bsoncxx_add_library TARGET OUTPUT_NAME LINK_TYPE)
     endif()
 
     if(BSONCXX_POLY_USE_MNMLSTC AND NOT BSONCXX_POLY_USE_SYSTEM_MNMLSTC)
-        add_dependencies(${TARGET} EP_mnmlstc_core)
-        ExternalProject_Get_Property(EP_mnmlstc_core source_dir)
         target_include_directories(
             ${TARGET}
             PUBLIC
-                $<BUILD_INTERFACE:${source_dir}/include>
-                $<BUILD_INTERFACE:${CMAKE_INSTALL_PREFIX}/${BSONCXX_HEADER_INSTALL_DIR}>
+                $<BUILD_INTERFACE:${CORE_INCLUDE_DIR}>
+                $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/bsoncxx/v_noabi/bsoncxx/third_party/mnmlstc>
         )
     elseif(BSONCXX_POLY_USE_BOOST)
         find_package(Boost 1.56.0 REQUIRED)
-        if(CMAKE_VERSION VERSION_LESS 3.15.0)
-            target_include_directories(${TARGET} PUBLIC ${Boost_INCLUDE_DIRS})
-        else()
-            target_link_libraries(${TARGET} PUBLIC Boost::boost)
-        endif()
+        target_link_libraries(${TARGET} PUBLIC Boost::boost)
     endif()
 
     target_link_libraries(${TARGET} PRIVATE ${libbson_target})
diff --git a/cmake/make_dist/MakeDist.cmake b/cmake/make_dist/MakeDist.cmake
index 53b61c5b08..68275d1262 100644
--- a/cmake/make_dist/MakeDist.cmake
+++ b/cmake/make_dist/MakeDist.cmake
@@ -17,9 +17,7 @@ include (MakeDistFiles)
 function (MAKE_DIST PACKAGE_PREFIX MONGOCXX_SOURCE_DIR BUILD_SOURCE_DIR)
 
    set (CMAKE_COMMAND_TMP "")
-   if (${CMAKE_VERSION} VERSION_GREATER 3.1)
-      set (CMAKE_COMMAND_TMP ${CMAKE_COMMAND} -E env)
-   endif ()
+   set (CMAKE_COMMAND_TMP ${CMAKE_COMMAND} -E env)
 
    # -- Remove any existing packaging directory.
 
diff --git a/cmake/make_dist/MakeDistCheck.cmake b/cmake/make_dist/MakeDistCheck.cmake
index 5bf2581d4d..d3647d2585 100644
--- a/cmake/make_dist/MakeDistCheck.cmake
+++ b/cmake/make_dist/MakeDistCheck.cmake
@@ -17,9 +17,7 @@ function (RUN_DIST_CHECK PACKAGE_PREFIX EXT)
    endif ()
 
    set (MY_CMAKE_COMMAND "")
-   if (${CMAKE_VERSION} VERSION_GREATER 3.1)
-      set (MY_CMAKE_COMMAND ${CMAKE_COMMAND} -E env)
-   endif ()
+   set (MY_CMAKE_COMMAND ${CMAKE_COMMAND} -E env)
 
    find_program (MAKE_COMMAND NAMES make gmake)
    if (${MAKE_COMMAND} STREQUAL "MAKE_COMMAND-NOTFOUND")
diff --git a/cmake/make_dist/MakeDistFiles.cmake b/cmake/make_dist/MakeDistFiles.cmake
index 24c1925353..6841933ecc 100644
--- a/cmake/make_dist/MakeDistFiles.cmake
+++ b/cmake/make_dist/MakeDistFiles.cmake
@@ -1,8 +1,3 @@
-
-if (${CMAKE_VERSION} VERSION_LESS 3.3)
-   include (CMakeParseArguments)
-endif ()
-
 function (SET_LOCAL_DIST output)
    set (dist_files "")
    foreach (file ${ARGN})
diff --git a/debian/patches/0002_skip_mnmlstc_extra_step.patch b/debian/patches/0002_skip_mnmlstc_extra_step.patch
deleted file mode 100644
index 3bb2750baa..0000000000
--- a/debian/patches/0002_skip_mnmlstc_extra_step.patch
+++ /dev/null
@@ -1,21 +0,0 @@
-Description: Remove an extra step in the MNMLSTC external project build; this is not used for official Debian packages and the step needs to be removed for users customizing the Debian package to build with MNMLSTC rather than Boost.
-Author: Roberto C. Sánchez <roberto@connexer.com>
-Forwarded: not-needed
---- a/src/bsoncxx/third_party/CMakeLists.txt
-+++ b/src/bsoncxx/third_party/CMakeLists.txt
-@@ -29,15 +29,6 @@
-         CMAKE_ARGS -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER} -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DBUILD_TESTING=Off -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_INSTALL_PREFIX}/${BSONCXX_HEADER_INSTALL_DIR}/bsoncxx/third_party/mnmlstc -DINCLUDE_INSTALL_DIR=.
-     )
- 
--    ExternalProject_Add_Step(
--        EP_mnmlstc_core
--        fix-includes
--        WORKING_DIRECTORY ${CMAKE_INSTALL_PREFIX}/${BSONCXX_HEADER_INSTALL_DIR}/bsoncxx/third_party/mnmlstc
--        COMMAND find . -type f | xargs perl -pi.bak -e "s|#include <core|#include <bsoncxx/third_party/mnmlstc/core|g"
--        COMMAND find . -name *.bak | xargs rm
--        DEPENDEES install
--    )
--
- endif()
- 
- set_dist_list (src_bsoncxx_third_party_DIST
diff --git a/debian/patches/series b/debian/patches/series
index 08ecb9dbf8..66be9b4817 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -1,2 +1 @@
 0001_remove_embedded_js.patch
-0002_skip_mnmlstc_extra_step.patch
diff --git a/debian/rules b/debian/rules
index 28dc01090f..cf9e469899 100755
--- a/debian/rules
+++ b/debian/rules
@@ -50,10 +50,6 @@ ifneq (,$(filter pkg.mongo-cxx-driver.mnmlstc,$(DEB_BUILD_PROFILES)))
 	mv $(CURDIR)/debian/tmp-mnmlstc/usr/include/bsoncxx/v_noabi/bsoncxx/third_party \
 	   $(CURDIR)/debian/tmp/usr/include/bsoncxx/v_noabi/bsoncxx/
 	rm -rf $(CURDIR)/debian/tmp-mnmlstc
-	# Fix MNMLSTC headers; handle the CMake external project step patched out
-	# by debian/patches/0002_skip_mnmlstc_extra_step.patch
-	( cd $(CURDIR)/debian/tmp/usr/include/bsoncxx/v_noabi/bsoncxx/third_party/mnmlstc; \
-	   find . -type f | xargs perl -pi -e "s|#include <core|#include <bsoncxx/third_party/mnmlstc/core|g" )
 endif
 
 override_dh_auto_test:
@@ -61,4 +57,3 @@ override_dh_auto_test:
 
 override_dh_missing:
 	dh_missing --fail-missing
-
diff --git a/docs/content/mongocxx-v3/installation/linux.md b/docs/content/mongocxx-v3/installation/linux.md
index 753e33a84f..cfcaf8e2be 100644
--- a/docs/content/mongocxx-v3/installation/linux.md
+++ b/docs/content/mongocxx-v3/installation/linux.md
@@ -85,18 +85,7 @@ cmake ..                                            \
 
 ### Step 4: Build and install the driver
 
-If you are using the default MNMLSTC polyfill and are installing to a
-directory requiring root permissions, you should install the polyfill with
-`sudo` before building the rest of mongocxx so you don't have to run
-the entire build with `sudo`:
-
-```sh
-# Only for MNMLSTC polyfill
-sudo cmake --build . --target EP_mnmlstc_core
-```
-
-Once MNMLSTC is installed, or if you are using a different polyfill,
-build and install the driver:
+Build and install the driver:
 
 ```sh
 cmake --build .
diff --git a/docs/content/mongocxx-v3/installation/macos.md b/docs/content/mongocxx-v3/installation/macos.md
index 6bbf2f7483..e56db7ced3 100644
--- a/docs/content/mongocxx-v3/installation/macos.md
+++ b/docs/content/mongocxx-v3/installation/macos.md
@@ -85,18 +85,7 @@ cmake ..                                            \
 
 ### Step 4: Build and install the driver
 
-If you are using the default MNMLSTC polyfill and are installing to a
-directory requiring root permissions, you should install the polyfill with
-`sudo` before building the rest of mongocxx so you don't have to run
-the entire build with `sudo`:
-
-```sh
-# Only for MNMLSTC polyfill
-sudo cmake --build . --target EP_mnmlstc_core
-```
-
-Once MNMLSTC is installed, or if you are using a different polyfill,
-build and install the driver:
+Build and install the driver:
 
 ```sh
 cmake --build .
diff --git a/examples/add_subdirectory/CMakeLists.txt b/examples/add_subdirectory/CMakeLists.txt
index 44ac158646..97f532577f 100644
--- a/examples/add_subdirectory/CMakeLists.txt
+++ b/examples/add_subdirectory/CMakeLists.txt
@@ -40,11 +40,7 @@ add_executable(hello_mongocxx hello_mongocxx.cpp)
 # Visual Studio pre 2017 requires boost polyfill.
 if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" AND CMAKE_CXX_STANDARD LESS 17)
   find_package(Boost 1.56.0 REQUIRED)
-  if (CMAKE_VERSION VERSION_LESS 3.15.0)
-    target_include_directories(hello_mongocxx PRIVATE ${Boost_INCLUDE_DIRS})
-  else()
-    target_link_libraries(hello_mongocxx PRIVATE Boost::boost)
-  endif()
+  target_link_libraries(hello_mongocxx PRIVATE Boost::boost)
 endif()
 
 target_link_libraries(hello_mongocxx
diff --git a/examples/projects/bsoncxx/cmake/shared/CMakeLists.txt b/examples/projects/bsoncxx/cmake/shared/CMakeLists.txt
index 5db2c05748..6a37c7a4ca 100644
--- a/examples/projects/bsoncxx/cmake/shared/CMakeLists.txt
+++ b/examples/projects/bsoncxx/cmake/shared/CMakeLists.txt
@@ -44,11 +44,7 @@ add_executable(hello_bsoncxx ../../hello_bsoncxx.cpp)
 if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     if (CMAKE_CXX_STANDARD LESS 17)
         find_package(Boost 1.56.0 REQUIRED)
-        if (CMAKE_VERSION VERSION_LESS 3.15.0)
-            target_include_directories(hello_bsoncxx PRIVATE ${Boost_INCLUDE_DIRS})
-        else()
-            target_link_libraries(hello_bsoncxx PRIVATE Boost::boost)
-        endif()
+        target_link_libraries(hello_bsoncxx PRIVATE Boost::boost)
         target_compile_definitions(hello_bsoncxx PRIVATE BSONCXX_POLY_USE_BOOST=ON)
     endif ()
 endif()
diff --git a/examples/projects/bsoncxx/cmake/static/CMakeLists.txt b/examples/projects/bsoncxx/cmake/static/CMakeLists.txt
index df422deb6c..b8d2d207b3 100644
--- a/examples/projects/bsoncxx/cmake/static/CMakeLists.txt
+++ b/examples/projects/bsoncxx/cmake/static/CMakeLists.txt
@@ -44,11 +44,7 @@ add_executable(hello_bsoncxx ../../hello_bsoncxx.cpp)
 if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     if (CMAKE_CXX_STANDARD LESS 17)
         find_package(Boost 1.56.0 REQUIRED)
-        if (CMAKE_VERSION VERSION_LESS 3.15.0)
-            target_include_directories(hello_bsoncxx PRIVATE ${Boost_INCLUDE_DIRS})
-        else()
-            target_link_libraries(hello_bsoncxx PRIVATE Boost::boost)
-        endif()
+        target_link_libraries(hello_bsoncxx PRIVATE Boost::boost)
         target_compile_definitions(hello_bsoncxx PRIVATE BSONCXX_POLY_USE_BOOST=ON)
     endif ()
 endif()
diff --git a/examples/projects/mongocxx/cmake/shared/CMakeLists.txt b/examples/projects/mongocxx/cmake/shared/CMakeLists.txt
index 1310fb3d82..e7df7c9bc7 100644
--- a/examples/projects/mongocxx/cmake/shared/CMakeLists.txt
+++ b/examples/projects/mongocxx/cmake/shared/CMakeLists.txt
@@ -44,11 +44,7 @@ add_executable(hello_mongocxx ../../hello_mongocxx.cpp)
 if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     if (CMAKE_CXX_STANDARD LESS 17)
         find_package(Boost 1.56.0 REQUIRED)
-        if (CMAKE_VERSION VERSION_LESS 3.15.0)
-            target_include_directories(hello_mongocxx PRIVATE ${Boost_INCLUDE_DIRS})
-        else()
-            target_link_libraries(hello_mongocxx PRIVATE Boost::boost)
-        endif()
+        target_link_libraries(hello_mongocxx PRIVATE Boost::boost)
         target_compile_definitions(hello_mongocxx PRIVATE BSONCXX_POLY_USE_BOOST=ON)
     endif ()
 endif()
diff --git a/examples/projects/mongocxx/cmake/static/CMakeLists.txt b/examples/projects/mongocxx/cmake/static/CMakeLists.txt
index cb0e6b9cf4..1827fced68 100644
--- a/examples/projects/mongocxx/cmake/static/CMakeLists.txt
+++ b/examples/projects/mongocxx/cmake/static/CMakeLists.txt
@@ -50,11 +50,7 @@ add_executable(hello_mongocxx ../../hello_mongocxx.cpp)
 if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     if (CMAKE_CXX_STANDARD LESS 17)
         find_package(Boost 1.56.0 REQUIRED)
-        if (CMAKE_VERSION VERSION_LESS 3.15.0)
-            target_include_directories(hello_mongocxx PRIVATE ${Boost_INCLUDE_DIRS})
-        else()
-            target_link_libraries(hello_mongocxx PRIVATE Boost::boost)
-        endif()
+        target_link_libraries(hello_mongocxx PRIVATE Boost::boost)
         target_compile_definitions(hello_mongocxx PRIVATE BSONCXX_POLY_USE_BOOST=ON)
     endif ()
 endif()
diff --git a/generate_uninstall/CMakeLists.txt b/generate_uninstall/CMakeLists.txt
index 3843ba24fe..26507a482f 100644
--- a/generate_uninstall/CMakeLists.txt
+++ b/generate_uninstall/CMakeLists.txt
@@ -19,14 +19,6 @@ if (WIN32)
       "${CMAKE_INSTALL_PREFIX}"
    )
    install (CODE "
-      if (EXISTS \${CMAKE_BINARY_DIR}/src/bsoncxx/third_party/EP_mnmlstc_core-prefix/src/EP_mnmlstc_core-build/install_manifest.txt)
-         file (
-            STRINGS
-               \${CMAKE_BINARY_DIR}/src/bsoncxx/third_party/EP_mnmlstc_core-prefix/src/EP_mnmlstc_core-build/install_manifest.txt
-               ADDL_MANIFEST_FILES
-         )
-         list (APPEND CMAKE_INSTALL_MANIFEST_FILES \${ADDL_MANIFEST_FILES})
-      endif ()
       string(REPLACE \";\" \"\\n\" MONGOCXX_INSTALL_MANIFEST_CONTENT
          \"\${CMAKE_INSTALL_MANIFEST_FILES}\")
       string(REPLACE \"/\" \"\\\\\" MONGOCXX_INSTALL_MANIFEST_CONTENT_WIN32
@@ -59,14 +51,6 @@ if (WIN32)
    )
 else ()
    install (CODE "
-      if (EXISTS \${CMAKE_BINARY_DIR}/src/bsoncxx/third_party/EP_mnmlstc_core-prefix/src/EP_mnmlstc_core-build/install_manifest.txt)
-         file (
-            STRINGS
-               \${CMAKE_BINARY_DIR}/src/bsoncxx/third_party/EP_mnmlstc_core-prefix/src/EP_mnmlstc_core-build/install_manifest.txt
-               ADDL_MANIFEST_FILES
-         )
-         list (APPEND CMAKE_INSTALL_MANIFEST_FILES \${ADDL_MANIFEST_FILES})
-      endif ()
       string(REPLACE \";\" \"\\n\" MONGOCXX_INSTALL_MANIFEST_CONTENT
          \"\${CMAKE_INSTALL_MANIFEST_FILES}\")
       file(WRITE \"mongocxx_install_manifest.txt\"
diff --git a/src/bsoncxx/CMakeLists.txt b/src/bsoncxx/CMakeLists.txt
index f30aea8364..32305fd82d 100644
--- a/src/bsoncxx/CMakeLists.txt
+++ b/src/bsoncxx/CMakeLists.txt
@@ -73,6 +73,24 @@ message ("bsoncxx version: ${BSONCXX_VERSION}")
 set(BSONCXX_INLINE_NAMESPACE "v${BSONCXX_ABI_VERSION}")
 set(BSONCXX_HEADER_INSTALL_DIR "${CMAKE_INSTALL_INCLUDEDIR}/bsoncxx/${BSONCXX_INLINE_NAMESPACE}" CACHE INTERNAL "")
 
+if (BSONCXX_POLY_USE_MNMLSTC AND NOT BSONCXX_POLY_USE_SYSTEM_MNMLSTC)
+    # For deprecated CMake package config files.
+    set(BSONCXX_POLY_MNMLSTC_DEPRECATED_INCLUDE_DIRS
+        [[list(PREPEND LIBBSONCXX_INCLUDE_DIRS "${PACKAGE_PREFIX_DIR}/include/bsoncxx/v_noabi/bsoncxx/third_party/mnmlstc")]]
+    )
+    set(BSONCXX_POLY_MNMLSTC_DEPRECATED_STATIC_INCLUDE_DIRS
+        [[list(PREPEND LIBBSONCXX_STATIC_INCLUDE_DIRS "${PACKAGE_PREFIX_DIR}/include/bsoncxx/v_noabi/bsoncxx/third_party/mnmlstc")]]
+    )
+
+    # For pkg-config files. Trailing space to separate cflags.
+    set(BSONCXX_POLY_MNMLSTC_PKGCONFIG_INCLUDE_DIRS
+        [[-I${includedir}/bsoncxx/v_noabi/bsoncxx/third_party/mnmlstc ]]
+    )
+    set(BSONCXX_POLY_MNMLSTC_PKGCONFIG_STATIC_INCLUDE_DIRS
+        [[-I${includedir}/bsoncxx/v_noabi/bsoncxx/third_party/mnmlstc ]]
+    )
+endif ()
+
 set(LIBBSON_REQUIRED_VERSION 1.24.0)
 set(LIBBSON_REQUIRED_ABI_VERSION 1.0)
 
diff --git a/src/bsoncxx/cmake/libbsoncxx-config.cmake.in b/src/bsoncxx/cmake/libbsoncxx-config.cmake.in
index eb6ace5427..ea6da4cb81 100644
--- a/src/bsoncxx/cmake/libbsoncxx-config.cmake.in
+++ b/src/bsoncxx/cmake/libbsoncxx-config.cmake.in
@@ -22,6 +22,7 @@ set(LIBBSONCXX_PACKAGE_VERSION @BSONCXX_VERSION@)
 @PACKAGE_INIT@
 
 set_and_check(LIBBSONCXX_INCLUDE_DIRS "${PACKAGE_PREFIX_DIR}/@PACKAGE_INCLUDE_INSTALL_DIRS@")
+@BSONCXX_POLY_MNMLSTC_DEPRECATED_INCLUDE_DIRS@
 
 # We want to provide an absolute path to the library and we know the
 # directory and the base name, but not the suffix, so we use CMake's
diff --git a/src/bsoncxx/cmake/libbsoncxx-static-config.cmake.in b/src/bsoncxx/cmake/libbsoncxx-static-config.cmake.in
index 0307621a44..7dcf9e5229 100644
--- a/src/bsoncxx/cmake/libbsoncxx-static-config.cmake.in
+++ b/src/bsoncxx/cmake/libbsoncxx-static-config.cmake.in
@@ -28,6 +28,7 @@ find_package(libbson-static-@LIBBSON_REQUIRED_ABI_VERSION@ @LIBBSON_REQUIRED_VER
 @PACKAGE_INIT@
 
 set_and_check(LIBBSONCXX_STATIC_INCLUDE_DIRS "${PACKAGE_PREFIX_DIR}/@PACKAGE_INCLUDE_INSTALL_DIRS@")
+@BSONCXX_POLY_MNMLSTC_DEPRECATED_STATIC_INCLUDE_DIRS@
 
 # We want to provide an absolute path to the library and we know the directory and the base name,
 # but not the suffix, so we use CMake's find_library() to pick that up.
diff --git a/src/bsoncxx/config/libbsoncxx-static.pc.in b/src/bsoncxx/config/libbsoncxx-static.pc.in
index 4505e00884..8df3b3cf7f 100644
--- a/src/bsoncxx/config/libbsoncxx-static.pc.in
+++ b/src/bsoncxx/config/libbsoncxx-static.pc.in
@@ -21,5 +21,5 @@ Description: The MongoDB C++11 BSON Library
 URL: http://github.com/mongodb/mongo-cxx-driver
 Version: @BSONCXX_VERSION@
 Requires: libbson-static-@LIBBSON_REQUIRED_ABI_VERSION@ >= @LIBBSON_REQUIRED_VERSION@
-Cflags: -I${includedir}/bsoncxx/@BSONCXX_INLINE_NAMESPACE@ -DBSONCXX_STATIC
+Cflags: @BSONCXX_POLY_MNMLSTC_PKGCONFIG_STATIC_INCLUDE_DIRS@-I${includedir}/bsoncxx/@BSONCXX_INLINE_NAMESPACE@ -DBSONCXX_STATIC
 Libs: -L${libdir} -lbsoncxx-static
diff --git a/src/bsoncxx/config/libbsoncxx.pc.in b/src/bsoncxx/config/libbsoncxx.pc.in
index 9d94bf31ef..760ab2ca9e 100644
--- a/src/bsoncxx/config/libbsoncxx.pc.in
+++ b/src/bsoncxx/config/libbsoncxx.pc.in
@@ -20,5 +20,5 @@ Name: libbsoncxx
 Description: The MongoDB C++11 BSON Library
 URL: http://github.com/mongodb/mongo-cxx-driver
 Version: @BSONCXX_VERSION@
-Cflags: -I${includedir}/bsoncxx/@BSONCXX_INLINE_NAMESPACE@
+Cflags: @BSONCXX_POLY_MNMLSTC_PKGCONFIG_INCLUDE_DIRS@-I${includedir}/bsoncxx/@BSONCXX_INLINE_NAMESPACE@
 Libs: -L${libdir} -lbsoncxx
diff --git a/src/bsoncxx/third_party/CMakeLists.txt b/src/bsoncxx/third_party/CMakeLists.txt
index c5156aa941..61856adb74 100644
--- a/src/bsoncxx/third_party/CMakeLists.txt
+++ b/src/bsoncxx/third_party/CMakeLists.txt
@@ -12,30 +12,97 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-include(ExternalProject)
+include(FetchContent)
 
 if (BSONCXX_POLY_USE_MNMLSTC AND NOT BSONCXX_POLY_USE_SYSTEM_MNMLSTC)
 
-    ExternalProject_Add(
+    set (core-src "${CMAKE_CURRENT_BINARY_DIR}/_deps/core-src")
+    set (core-subbuild "${CMAKE_CURRENT_BINARY_DIR}/_deps/core-subbuild")
+    set (core-build "${CMAKE_CURRENT_BINARY_DIR}/_deps/core-build")
+    set (core-install "${CMAKE_CURRENT_BINARY_DIR}/_deps/core-install")
+
+    FetchContent_Declare(
         EP_mnmlstc_core
+
+        SOURCE_DIR "${core-src}"
+        SUBBUILD_DIR "${core-subbuild}"
+        BINARY_DIR "${core-build}"
+        INSTALL_DIR "${core-install}"
+
         GIT_REPOSITORY https://github.com/mnmlstc/core
         GIT_TAG v1.1.0
+        GIT_SHALLOW TRUE
         LOG_DOWNLOAD ON
-        LOG_CONFIGURE ON
-        LOG_BUILD ON
-        LOG_INSTALL ON
-        LOG_UPDATE ON
-        UPDATE_COMMAND ""
-        CMAKE_ARGS -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER} -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DBUILD_TESTING=Off -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_INSTALL_PREFIX}/${BSONCXX_HEADER_INSTALL_DIR}/bsoncxx/third_party/mnmlstc -DINCLUDE_INSTALL_DIR=.
+
+        FETCHCONTENT_UPDATES_DISCONNECTED ON
     )
+    FetchContent_GetProperties (EP_mnmlstc_core)
 
-    ExternalProject_Add_Step(
-        EP_mnmlstc_core
-        fix-includes
-        WORKING_DIRECTORY ${CMAKE_INSTALL_PREFIX}/${BSONCXX_HEADER_INSTALL_DIR}/bsoncxx/third_party/mnmlstc
-        COMMAND find . -type f | xargs perl -pi.bak -e "s|#include <core|#include <bsoncxx/third_party/mnmlstc/core|g"
-        COMMAND find . -name *.bak | xargs rm
-        DEPENDEES install
+    find_package (core NO_DEFAULT_PATH PATHS "${core-install}" QUIET)
+
+    if (core_FOUND AND "$CACHE{INTERNAL_MONGOC_MNMLSTC_CORE_FOUND}")
+        # The mnmlstc/core library is already populated and up-to-date.
+    else ()
+        if (NOT ep_mnmlstc_core_POPULATED)
+            message (STATUS "Downloading mnmlstc/core...")
+            FetchContent_Populate (EP_mnmlstc_core)
+            message (STATUS "Downloading mnmlstc/core... done.")
+        endif ()
+
+        message (STATUS "Configuring mnmlstc/core...")
+        execute_process (
+           COMMAND
+              "${CMAKE_COMMAND}"
+                 "-S" "${core-src}"
+                 "-B" "${core-build}"
+                 "-DCMAKE_INSTALL_PREFIX=${core-install}"
+                 "-DBUILD_TESTING=OFF"
+                 "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}"
+                 "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
+           RESULT_VARIABLE retval
+        )
+        if (NOT "${retval}" STREQUAL "0")
+           message (FATAL_ERROR "execute_process() fatal error: ${retval}")
+        endif ()
+        message (STATUS "Configuring mnmlstc/core... done.")
+
+        message (STATUS "Building mnmlstc/core...")
+        execute_process (
+           COMMAND
+              "${CMAKE_COMMAND}"
+                 --build "${core-build}"
+                 --config "${CMAKE_BUILD_TYPE}"
+           RESULT_VARIABLE retval
+        )
+        if (NOT "${retval}" STREQUAL "0")
+           message (FATAL_ERROR "execute_process() fatal error: ${retval}")
+        endif ()
+        message (STATUS "Building mnmlstc/core... done.")
+
+        message (STATUS "Installing mnmlstc/core...")
+        execute_process (
+           COMMAND
+              "${CMAKE_COMMAND}"
+                 --install "${core-build}"
+                 --config "${CMAKE_BUILD_TYPE}"
+           RESULT_VARIABLE retval
+        )
+        if (NOT "${retval}" STREQUAL "0")
+           message (FATAL_ERROR "execute_process() fatal error: ${retval}")
+        endif ()
+        message (STATUS "Installing mnmlstc/core... done.")
+
+        find_package (core REQUIRED NO_DEFAULT_PATH PATHS "${core-install}")
+
+        # Ensure the mnmlstc/core CMake configuration is also (re)configured if the cache is fresh.
+        set (INTERNAL_MONGOC_MNMLSTC_CORE_FOUND TRUE CACHE INTERNAL "")
+    endif ()
+
+    set (CORE_INCLUDE_DIR "${CORE_INCLUDE_DIR}" PARENT_SCOPE)
+
+    install (
+        DIRECTORY "${core-install}/include/"
+        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/bsoncxx/v_noabi/bsoncxx/third_party/mnmlstc"
     )
 
 endif()