diff --git a/pkgs/build-support/cc-wrapper/cc-wrapper.sh b/pkgs/build-support/cc-wrapper/cc-wrapper.sh
index 83b6817798f26..be128044df7cb 100644
--- a/pkgs/build-support/cc-wrapper/cc-wrapper.sh
+++ b/pkgs/build-support/cc-wrapper/cc-wrapper.sh
@@ -122,10 +122,10 @@ fi
 
 if [[ "$isCxx" = 1 ]]; then
     if [[ "$cxxInclude" = 1 ]]; then
-        NIX_CFLAGS_COMPILE_@suffixSalt@+=" $NIX_CXXSTDLIB_COMPILE_@suffixSalt@"
+        NIX_CFLAGS_COMPILE_@suffixSalt@="$NIX_CXXSTDLIB_COMPILE_@suffixSalt@ $NIX_CFLAGS_COMPILE_@suffixSalt@"
     fi
     if [[ "$cxxLibrary" = 1 ]]; then
-        NIX_CFLAGS_LINK_@suffixSalt@+=" $NIX_CXXSTDLIB_LINK_@suffixSalt@"
+        NIX_CFLAGS_LINK_@suffixSalt@="$NIX_CXXSTDLIB_LINK_@suffixSalt@ $NIX_CFLAGS_LINK_@suffixSalt@"
     fi
 fi
 
diff --git a/pkgs/development/tools/clang-tools/wrapper b/pkgs/development/tools/clang-tools/wrapper
index 1008023fdc0d1..178cd59ac05f9 100755
--- a/pkgs/development/tools/clang-tools/wrapper
+++ b/pkgs/development/tools/clang-tools/wrapper
@@ -20,8 +20,8 @@ buildcpath() {
 
 export CPATH=${CPATH}${CPATH:+':'}$(buildcpath ${NIX_CFLAGS_COMPILE} \
                                                $(<@clang@/nix-support/libc-cflags)):@clang@/resource-root/include
-export CPLUS_INCLUDE_PATH=${CPLUS_INCLUDE_PATH}${CPLUS_INCLUDE_PATH:+':'}$(buildcpath ${NIX_CFLAGS_COMPILE} \
-                                                                                      $(<@clang@/nix-support/libcxx-cxxflags) \
+export CPLUS_INCLUDE_PATH=${CPLUS_INCLUDE_PATH}${CPLUS_INCLUDE_PATH:+':'}$(buildcpath $(<@clang@/nix-support/libcxx-cxxflags) \
+                                                                                      ${NIX_CFLAGS_COMPILE} \
                                                                                       $(<@clang@/nix-support/libc-cflags)):@clang@/resource-root/include
 
 exec -a "$0" @unwrapped@/bin/$(basename $0) "$@"