diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index d4870457bb2..e878553795c 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -1680,7 +1680,7 @@ BytecodeEmitter::bindNameToSlotHelper(ParseNode* pn)
 
     if (dn->pn_cookie.isFree()) {
         if (evalCaller) {
-            MOZ_ASSERT(script->compileAndGo());
+            MOZ_ASSERT(script->treatAsRunOnce() || sc->isFunctionBox());
 
             /*
              * Don't generate upvars on the left side of a for loop. See
@@ -2073,12 +2073,18 @@ BytecodeEmitter::isInLoop()
 bool
 BytecodeEmitter::checkSingletonContext()
 {
-    if (!script->compileAndGo() || sc->isFunctionBox() || isInLoop())
+    if (!script->treatAsRunOnce() || sc->isFunctionBox() || isInLoop())
         return false;
     hasSingletons = true;
     return true;
 }
 
+bool
+BytecodeEmitter::checkRunOnceContext()
+{
+    return checkSingletonContext() || (!isInLoop() && isRunOnceLambda());
+}
+
 bool
 BytecodeEmitter::needsImplicitThis()
 {
@@ -5194,10 +5200,7 @@ BytecodeEmitter::emitFunction(ParseNode* pn, bool needsProto)
      * make a deep clone of its contents.
      */
     if (fun->isInterpreted()) {
-        bool singleton =
-            script->compileAndGo() &&
-            fun->isInterpreted() &&
-            (checkSingletonContext() || (!isInLoop() && isRunOnceLambda()));
+        bool singleton = checkRunOnceContext();
         if (!JSFunction::setTypeForScriptedFunction(cx, fun, singleton))
             return false;
 
@@ -6088,7 +6091,7 @@ BytecodeEmitter::emitCallOrNew(ParseNode* pn)
          * will just cause the inner scripts to be repeatedly cloned.
          */
         MOZ_ASSERT(!emittingRunOnceLambda);
-        if (checkSingletonContext() || (!isInLoop() && isRunOnceLambda())) {
+        if (checkRunOnceContext()) {
             emittingRunOnceLambda = true;
             if (!emitTree(pn2))
                 return false;
diff --git a/js/src/frontend/BytecodeEmitter.h b/js/src/frontend/BytecodeEmitter.h
index 4e8dacf1ac9..0a0c95889d2 100644
--- a/js/src/frontend/BytecodeEmitter.h
+++ b/js/src/frontend/BytecodeEmitter.h
@@ -248,6 +248,10 @@ struct BytecodeEmitter
     bool isInLoop();
     bool checkSingletonContext();
 
+    // Check whether our function is in a run-once context (a toplevel
+    // run-one script or a run-once lambda).
+    bool checkRunOnceContext();
+
     bool needsImplicitThis();
 
     void tellDebuggerAboutCompiledScript(ExclusiveContext* cx);
diff --git a/js/src/vm/Xdr.h b/js/src/vm/Xdr.h
index 840efda8c7e..ce5be503d24 100644
--- a/js/src/vm/Xdr.h
+++ b/js/src/vm/Xdr.h
@@ -29,7 +29,7 @@ namespace js {
  *
  *  https://developer.mozilla.org/en-US/docs/SpiderMonkey/Internals/Bytecode
  */
-static const uint32_t XDR_BYTECODE_VERSION_SUBTRAHEND = 270;
+static const uint32_t XDR_BYTECODE_VERSION_SUBTRAHEND = 271;
 static const uint32_t XDR_BYTECODE_VERSION =
     uint32_t(0xb973c0de - XDR_BYTECODE_VERSION_SUBTRAHEND);