--- a/js/src/jsscript.cpp
+++ b/js/src/jsscript.cpp
@@ -530,16 +530,29 @@ js_XDRScript(JSXDRState *xdr, JSScript *
     ok = JS_XDRBytes(xdr, (char *) code, length * sizeof(jsbytecode));
 
     if (code != script->code)
         JS_free(cx, code);
 
     if (!ok)
         goto error;
 
+    jsbytecode *pc = code;
+    jsbytecode *end = pc + length;
+    while (pc < end) {
+        JSOp op = (JSOp)*pc;
+        int len = js_CodeSpec[op].length;
+        if (!len)
+            goto error;
+        /* Assign a new loop table slot for every JSOP_HEADER opcode. */
+        if (op == JSOP_HEADER) 
+            SET_UINT24(pc + 1, js_AllocateLoopTableSlot(cx->runtime));
+        pc += len;
+    }
+    
     if (!JS_XDRBytes(xdr, (char *)notes, nsrcnotes * sizeof(jssrcnote)) ||
         !JS_XDRCStringOrNull(xdr, (char **)&script->filename) ||
         !JS_XDRUint32(xdr, &lineno) ||
         !JS_XDRUint32(xdr, &depth)) {
         goto error;
     }
 
     if (xdr->mode == JSXDR_ENCODE) {