diff --git a/mozilla/js/src/jsemit.c b/mozilla/js/src/jsemit.c
index c793bc1a882..eea0b2f850f 100644
--- a/mozilla/js/src/jsemit.c
+++ b/mozilla/js/src/jsemit.c
@@ -5336,6 +5336,20 @@ js_EmitTree(JSContext *cx, JSCodeGenerator *cg, JSParseNode *pn)
         pn2 = pn->pn_kid;
         JS_ASSERT(pn2->pn_type != TOK_RP);
         op = pn->pn_op;
+
+        /*
+         * Allocate another stack slot for GC protection in case the initial
+         * value being post-incremented or -decremented is not a number, but
+         * converts to a jsdouble.  In the TOK_NAME cases, op has 0 operand
+         * uses and 1 definition, so we don't need an extra stack slot -- we
+         * can use the one allocated for the def.
+         */
+        if (pn2->pn_type != TOK_NAME &&
+            (js_CodeSpec[op].format & JOF_POST) &&
+            (uintN)++cg->stackDepth > cg->maxStackDepth) {
+            cg->maxStackDepth = cg->stackDepth;
+        }
+
         switch (pn2->pn_type) {
           case TOK_NAME:
             pn2->pn_op = op;
@@ -5391,18 +5405,8 @@ js_EmitTree(JSContext *cx, JSCodeGenerator *cg, JSParseNode *pn)
             JS_ASSERT(0);
         }
 
-        /*
-         * Allocate another stack slot for GC protection in case the initial
-         * value being post-incremented or -decremented is not a number, but
-         * converts to a jsdouble.  In the TOK_NAME cases, op has 0 operand
-         * uses and 1 definition, so we don't need an extra stack slot -- we
-         * can use the one allocated for the def.
-         */
-        if (pn2->pn_type != TOK_NAME &&
-            (js_CodeSpec[op].format & JOF_POST) &&
-            (uintN)cg->stackDepth == cg->maxStackDepth) {
-            ++cg->maxStackDepth;
-        }
+        if (pn2->pn_type != TOK_NAME && (js_CodeSpec[op].format & JOF_POST))
+            --cg->stackDepth;
         break;
 
       case TOK_DELETE: