diff --git a/src/xpdev/dirwrap.c b/src/xpdev/dirwrap.c
index e025272db0334df4bb23fb5b53b7dc596a853114..9a6e31eae9f8b6806bdbe7d86e35623eae978dce 100644
--- a/src/xpdev/dirwrap.c
+++ b/src/xpdev/dirwrap.c
@@ -1032,7 +1032,7 @@ BOOL DLLCALL isfullpath(const char* filename)
 {
 	return(filename[0]=='/'
 #ifdef WIN32
-		|| filename[0]=='\\' || filename[1]==':'
+		|| filename[0]=='\\' || (isalpha(filename[0] && filename[1]==':')
 #endif
 		);
 }