diff --git a/src/xdiff/xinclude.h b/src/xdiff/xinclude.h
index 21ae35e..6e9f50a 100644
--- a/src/xdiff/xinclude.h
+++ b/src/xdiff/xinclude.h
@@ -33,7 +33,7 @@
 
 // Mark unused function arguments with UNUSED, so that gcc -Wunused-parameter
 // can be used to check for mistakes.
-#ifdef HAVE_ATTRIBUTE_UNUSED
+#if defined(HAVE_ATTRIBUTE_UNUSED) || defined(__MINGW32__)
 # define UNUSED __attribute__((unused))
 #else
 # define UNUSED