diff --git a/src/diff.c b/src/diff.c
index 6c13d2a..a46f0bf 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -726,10 +726,7 @@
 clear_diffin(diffin_T *din)
 {
     if (din->din_fname == NULL)
-    {
-	vim_free(din->din_mmfile.ptr);
-	din->din_mmfile.ptr = NULL;
-    }
+	VIM_CLEAR(din->din_mmfile.ptr);
     else
 	mch_remove(din->din_fname);
 }