diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 89c03a13b76..7718adb72cd 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -1124,7 +1124,7 @@ def concretize(self):
 
         for s in self.traverse(root=False):
             if s.external_module:
-                compiler = spack.compilers.compiler_for_spec(s.compiler, s.architecture.platform_os)
+                compiler = spack.compilers.compiler_for_spec(s.compiler, s.architecture)
                 for mod in compiler.modules:
                     load_module(mod)