diff --git a/src/os_mswin.c b/src/os_mswin.c
index 360c456..b6393db 100644
--- a/src/os_mswin.c
+++ b/src/os_mswin.c
@@ -389,6 +389,8 @@
     // Another way to check is to use mch_FullName() and see if the result is
     // the same as the name or mch_FullName() fails.  However, this has quite a
     // bit of overhead, so let's not do that.
+    if (*fname == NUL)
+	return TRUE;
     return ((ASCII_ISALPHA(fname[0]) && fname[1] == ':'
 				      && (fname[2] == '/' || fname[2] == '\\'))
 	    || (fname[0] == fname[1] && (fname[0] == '/' || fname[0] == '\\')));