--- a/make_cffi.py
+++ b/make_cffi.py
@@ -43,7 +43,7 @@
 # Distutils doesn't always set compiler.preprocessor, so invoke the
 # preprocessor manually when needed.
 args = getattr(compiler, "preprocessor", None)
-if compiler.compiler_type == "unix":
+if compiler.compiler_type == "mingw32":
     if not args:
         # Using .compiler respects the CC environment variable.
         args = [compiler.compiler[0], "-E"]
