diff --git a/Makefile.pre.in b/Makefile.pre.in
index 258236d3645096..af9504dfac7f3b 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -472,7 +472,7 @@ profile-opt:
 	$(MAKE) profile-removal
 
 build_all_generate_profile:
-	$(MAKE) @DEF_MAKE_RULE@ CFLAGS_NODIST="$(CFLAGS) $(PGO_PROF_GEN_FLAG)" LDFLAGS="$(LDFLAGS) $(PGO_PROF_GEN_FLAG)" LIBS="$(LIBS)"
+	$(MAKE) @DEF_MAKE_RULE@ CFLAGS_NODIST="$(CFLAGS_NODIST) $(PGO_PROF_GEN_FLAG)" LDFLAGS="$(LDFLAGS) $(PGO_PROF_GEN_FLAG)" LIBS="$(LIBS)"
 
 run_profile_task:
 	: # FIXME: can't run for a cross build
@@ -482,7 +482,7 @@ build_all_merge_profile:
 	$(LLVM_PROF_MERGER)
 
 build_all_use_profile:
-	$(MAKE) @DEF_MAKE_RULE@ CFLAGS_NODIST="$(CFLAGS) $(PGO_PROF_USE_FLAG)" LDFLAGS="$(LDFLAGS)"
+	$(MAKE) @DEF_MAKE_RULE@ CFLAGS_NODIST="$(CFLAGS_NODIST) $(PGO_PROF_USE_FLAG)" LDFLAGS="$(LDFLAGS)"
 
 # Compile and run with gcov
 .PHONY=coverage coverage-lcov coverage-report
diff --git a/Misc/NEWS.d/next/Build/2018-12-14-19-36-05.bpo-35499.9yAldM.rst b/Misc/NEWS.d/next/Build/2018-12-14-19-36-05.bpo-35499.9yAldM.rst
new file mode 100644
index 00000000000000..ed730b9d9b4a49
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2018-12-14-19-36-05.bpo-35499.9yAldM.rst
@@ -0,0 +1,3 @@
+``make profile-opt`` no longer replaces ``CFLAGS_NODIST`` with ``CFLAGS``. It
+now adds profile-guided optimization (PGO) flags to ``CFLAGS_NODIST``: existing
+``CFLAGS_NODIST`` flags are kept.