diff --git a/pkgs/development/compilers/llvm/git/libcxx/default.nix b/pkgs/development/compilers/llvm/git/libcxx/default.nix
index 84902c68eda32..af4bd85a1b6df 100644
--- a/pkgs/development/compilers/llvm/git/libcxx/default.nix
+++ b/pkgs/development/compilers/llvm/git/libcxx/default.nix
@@ -74,7 +74,13 @@ stdenv.mkDerivation rec {
       "-DLIBCXX_ENABLE_THREADS=OFF"
       "-DLIBCXX_ENABLE_FILESYSTEM=OFF"
       "-DLIBCXX_ENABLE_EXCEPTIONS=OFF"
-    ] ++ lib.optional (!enableShared) "-DLIBCXX_ENABLE_SHARED=OFF";
+    ] ++ lib.optional (!enableShared) "-DLIBCXX_ENABLE_SHARED=OFF"
+    # If we're only building the headers we don't actually *need* a functioning
+    # C/C++ compiler:
+    ++ lib.optionals (headersOnly) [
+      "-DCMAKE_C_COMPILER_WORKS=ON"
+      "-DCMAKE_CXX_COMPILER_WORKS=ON"
+    ];
 
   ninjaFlags = lib.optional headersOnly "generate-cxx-headers";
   installTargets = lib.optional headersOnly "install-cxx-headers";