diff --git a/kikit/panelize.py b/kikit/panelize.py
index 14a121d0..a13e534d 100644
--- a/kikit/panelize.py
+++ b/kikit/panelize.py
@@ -618,7 +618,7 @@ def makeLayersVisible(self):
             pass
 
     def writeCustomDrcRules(self):
-        with open(self.getDruFilepath(), "w", encoding="utf-8") as f:
+        with open(self.getDruFilepath(), "w+", encoding="utf-8") as f:
             f.write("(version 1)\n\n")
             for r in self.customDRCRules:
                 f.write(str(r))