diff --git a/Tools/scripts/patchtool.py b/Tools/scripts/patchtool.py
index 08f8f528851d..845a7ff92c6c 100755
--- a/Tools/scripts/patchtool.py
+++ b/Tools/scripts/patchtool.py
@@ -157,6 +157,8 @@ def getrelpath(path, wrksrc):
 	path = os.path.abspath(path)
 	wrksrc = os.path.abspath(wrksrc)
 	commonpart = os.path.commonprefix((path, wrksrc))
+	while commonpart[-1:] != '/':
+		commonpart = commonpart[:-1]
 	path = path[len(commonpart):]
 	wrksrc = wrksrc[len(commonpart):]
 	if wrksrc == '':