diff --git a/lib/spack/spack/directives.py b/lib/spack/spack/directives.py
index b69f83a75d..6c929007ba 100644
--- a/lib/spack/spack/directives.py
+++ b/lib/spack/spack/directives.py
@@ -97,7 +97,7 @@ class OpenMpi(Package):
 PatchesType = Optional[Union[Patcher, str, List[Union[Patcher, str]]]]
 
 
-SUPPORTED_LANGUAGES = ("fortran", "cxx")
+SUPPORTED_LANGUAGES = ("fortran", "cxx", "c")
 
 
 def _make_when_spec(value: WhenType) -> Optional["spack.spec.Spec"]: