diff --git a/depends/packages/bdb.mk b/depends/packages/bdb.mk
index cd41a3f8fc..304887d815 100644
--- a/depends/packages/bdb.mk
+++ b/depends/packages/bdb.mk
@@ -12,7 +12,7 @@ define $(package)_set_vars
   $(package)_config_opts_mingw32=--enable-mingw
   $(package)_config_opts_linux=--with-pic
   $(package)_cflags+=-Wno-error=implicit-function-declaration
-  $(package)_cxxflags=-std=c++17
+  $(package)_cxxflags+=-std=c++17
   $(package)_cxxflags_aarch64_linux = $(GCCFLAGS)
   $(package)_cflags_aarch64_linux = $(GCCFLAGS)
   $(package)_cxxflags_arm_linux = $(GCCFLAGS)
diff --git a/depends/packages/bdb53.mk b/depends/packages/bdb53.mk
index f3f63cdd23..35ee47c3ab 100644
--- a/depends/packages/bdb53.mk
+++ b/depends/packages/bdb53.mk
@@ -12,7 +12,7 @@ define $(package)_set_vars
   $(package)_config_opts_mingw32=--enable-mingw
   $(package)_config_opts_linux=--with-pic
   $(package)_cflags+=-Wno-error=implicit-function-declaration
-  $(package)_cxxflags=-std=c++17
+  $(package)_cxxflags+=-std=c++17
   $(package)_cxxflags_aarch64_linux = $(GCCFLAGS)
   $(package)_cflags_aarch64_linux = $(GCCFLAGS)
   $(package)_cxxflags_arm_linux = $(GCCFLAGS)
diff --git a/depends/packages/boost.mk b/depends/packages/boost.mk
index 93a8f52738..a293a6a8c8 100644
--- a/depends/packages/boost.mk
+++ b/depends/packages/boost.mk
@@ -28,7 +28,7 @@ ifneq (,$(findstring clang,$($(package)_cxx)))
 endif
 $(package)_archiver_$(host_os)=$($(package)_ar)
 $(package)_config_libraries=filesystem,system,thread,test,iostreams
-$(package)_cxxflags=-std=c++17 -fvisibility=hidden
+$(package)_cxxflags+=-std=c++17 -fvisibility=hidden
 $(package)_cxxflags_linux=-fPIC
 $(package)_cxxflags_android=-fPIC
 endef