diff --git a/pkgs/development/libraries/gsm/default.nix b/pkgs/development/libraries/gsm/default.nix
index 13088dda0c91..f70a748a20e7 100644
--- a/pkgs/development/libraries/gsm/default.nix
+++ b/pkgs/development/libraries/gsm/default.nix
@@ -18,6 +18,8 @@ stdenv.mkDerivation rec {
   };
 
   patchPhase = ''
+    substituteInPlace Makefile \
+      --replace "= gcc " "?= gcc "
     # Fix include directory
     sed -e 's,$(GSM_INSTALL_ROOT)/inc,$(GSM_INSTALL_ROOT)/include/gsm,' -i Makefile
   '' + optionalString (!staticSupport) (