diff --git a/src/or/control.c b/src/or/control.c
index 564bb1b396..80ad6a33b3 100644
--- a/src/or/control.c
+++ b/src/or/control.c
@@ -481,7 +481,7 @@ decode_hashed_password(char *buf, const char *hashed)
       }
   }
   if (buf)
-    memcpy(buf, decoded, sizeof(decoded));
+    memcpy(buf, decoded, S2K_SPECIFIER_LEN+DIGEST_LEN);
   return 0;
 }