diff --git a/pkgs/development/compilers/graalvm/default.nix b/pkgs/development/compilers/graalvm/default.nix
index 61e3b6c16aee..41cf956cd9f9 100644
--- a/pkgs/development/compilers/graalvm/default.nix
+++ b/pkgs/development/compilers/graalvm/default.nix
@@ -293,7 +293,7 @@ in rec {
                     # gfortran readline bzip2 lzma pcre.dev curl ed ## WIP: fastr dependencies
                   ];
     postUnpack = ''
-      cp ${stdenv.cc.cc}/include/c++/${stdenv.cc.cc.version}/stdlib.h \
+      cp ${stdenv.cc.cc}/include/c++/${lib.getVersion stdenv.cc.cc}/stdlib.h \
         $sourceRoot/sulong/projects/com.oracle.truffle.llvm.libraries.bitcode/include
       cp ${truffleMake} $TMP && mv *truffle.make truffle.make
       rm $sourceRoot/truffle/src/libffi/patches/others/0001-Add-mx-bootstrap-Makefile.patch
@@ -318,7 +318,7 @@ in rec {
         --replace 'protected String compilerCommand = "cc";' 'protected String compilerCommand = "${stdenv.cc}/bin/cc";'
       # prevent cyclical imports caused by identical <include> names
       substituteInPlace sulong/projects/com.oracle.truffle.llvm.libraries.bitcode/include/stdlib.h \
-        --replace '# include <cstdlib>' '# include "${stdenv.cc.cc}/include/c++/${stdenv.cc.cc.version}/cstdlib"'
+        --replace '# include <cstdlib>' '# include "${stdenv.cc.cc}/include/c++/${lib.getVersion stdenv.cc.cc}/cstdlib"'
       # dragonegg can't seem to compile on nix, so let's not require it
       substituteInPlace sulong/mx.sulong/suite.py \
         --replace '"requireDragonegg" : True,' '"requireDragonegg" : False,'