diff --git a/gcd.py b/gcd.py
index 9584e2e..c47b194 100644
--- a/gcd.py
+++ b/gcd.py
@@ -170,7 +170,7 @@ with open(FILE, "rb") as f:
             #print("  > " + repr(payloadshort))
         add_to_cksum(payload)
         if ttype in [0x0505, 0x02bd]:
-            with open("fw_{:04x}.bin".format(ttype), "ab") as of:
+            with open("{}_{:04x}.bin".format(FILE, ttype), "ab") as of:
                 of.write(payload)
         i = i + 1