diff --git a/js/src/jsinterp.cpp b/js/src/jsinterp.cpp
index 4aeb2ac550b..34e8b22aabf 100644
--- a/js/src/jsinterp.cpp
+++ b/js/src/jsinterp.cpp
@@ -428,10 +428,13 @@ js::RunScript(JSContext *cx, JSScript *script, StackFrame *fp)
     JS_ASSERT(script);
     JS_ASSERT(fp == cx->fp());
     JS_ASSERT(fp->script() == script);
+    JS_ASSERT_IF(!fp->isGeneratorFrame(), cx->regs().pc == script->code);
 #ifdef JS_METHODJIT_SPEW
     JMCheckLogging();
 #endif
 
+    JS_CHECK_RECURSION(cx, return false);
+
     /* FIXME: Once bug 470510 is fixed, make this an assert. */
     if (script->compileAndGo) {
         if (fp->scopeChain().global().isCleared()) {
@@ -1567,9 +1570,6 @@ js::Interpret(JSContext *cx, StackFrame *entryFrame, InterpMode interpMode)
     int32_t len;
     len = 0;
 
-    /* Check for too deep of a native thread stack. */
-    JS_CHECK_RECURSION(cx, goto error);
-
     DO_NEXT_OP(len);
 
 #if JS_THREADED_INTERP
@@ -4028,6 +4028,9 @@ END_CASE(JSOP_ARRAYPUSH)
     JS_ASSERT(&cx->regs() == &regs);
     JS_ASSERT(uint32_t(regs.pc - script->code) < script->length);
 
+    /* When rejoining, we must not err before finishing Interpret's prologue. */
+    JS_ASSERT(interpMode != JSINTERP_REJOIN);
+
     if (cx->isExceptionPending()) {
         /* Restore atoms local in case we will resume. */
         atoms = script->atoms;
diff --git a/js/src/methodjit/InvokeHelpers.cpp b/js/src/methodjit/InvokeHelpers.cpp
index e92929fb32e..e36d7add87b 100644
--- a/js/src/methodjit/InvokeHelpers.cpp
+++ b/js/src/methodjit/InvokeHelpers.cpp
@@ -367,7 +367,9 @@ UncachedInlineCall(VMFrame &f, InitialFrameFlags initial,
         regs.fp()->resetInlinePrev(f.fp(), f.regs.pc);
     }
 
-    bool ok = !!Interpret(cx, cx->fp());
+    JS_CHECK_RECURSION(cx, return false);
+
+    bool ok = Interpret(cx, cx->fp());
     f.cx->stack.popInlineFrame(regs);
 
     if (ok)