diff --git a/Modules/gdbmmodule.c b/Modules/gdbmmodule.c
index 025bdb7dba0..76d54f820b1 100644
--- a/Modules/gdbmmodule.c
+++ b/Modules/gdbmmodule.c
@@ -97,6 +97,7 @@ dbm_length(dbmobject *dp)
         datum key,okey;
         int size;
         okey.dsize=0;
+        okey.dptr=NULL;
 
         size = 0;
         for (key=gdbm_firstkey(dp->di_dbm); key.dptr;