diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index a816402c1..998e8027e 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -5502,7 +5502,7 @@ BytecodeEmitter::emitIterator()
 bool
 BytecodeEmitter::emitForInOrOfVariables(ParseNode* pn)
 {
-    MOZ_ASSERT(pn->isKind(PNK_VAR) || pn->isKind(PNK_LET));
+    MOZ_ASSERT(pn->isKind(PNK_VAR) || pn->isKind(PNK_LET) || pn->isKind(PNK_CONST));
 
     // ES6 specifies that loop variables get a fresh binding in each iteration.
     // This is currently implemented for C-style for(;;) loops, but not
@@ -5524,7 +5524,7 @@ BytecodeEmitter::emitForInOrOfVariables(ParseNode* pn)
         if (!emitVariables(pn, DefineVars))
             return false;
     } else {
-        MOZ_ASSERT(pn->isKind(PNK_LET));
+        MOZ_ASSERT(pn->isKind(PNK_LET) || pn->isKind(PNK_CONST));
         if (!emitVariables(pn, InitializeVars))
             return false;
     }
diff --git a/js/src/frontend/Parser.cpp b/js/src/frontend/Parser.cpp
index 5830e7d90..78852eff7 100644
--- a/js/src/frontend/Parser.cpp
+++ b/js/src/frontend/Parser.cpp
@@ -4581,12 +4581,15 @@ Parser<ParseHandler>::declarationPattern(Node decl, TokenKind tt, BindData<Parse
             *forHeadKind = PNK_FORHEAD;
 
         if (*forHeadKind != PNK_FORHEAD) {
+// TenFourFox issue 541
+#if(0)
             // |for (const ... in ...);| and |for (const ... of ...);| are
             // syntax errors for now.  We'll fix this in bug 449811.
             if (handler.declarationIsConst(decl)) {
                 report(ParseError, false, pattern, JSMSG_BAD_CONST_DECL);
                 return null();
             }
+#endif
 
             if (!checkDestructuringPattern(data, pattern))
                 return null();
@@ -4786,9 +4789,14 @@ Parser<ParseHandler>::declarationName(Node decl, TokenKind tt, BindData<ParseHan
                 return null();
 
             if (isForIn || isForOf) {
+// TenFourFox issue 541
+#if(0)
                 // XXX Uncomment this when fixing bug 449811.  Until then,
                 //     |for (const ... in/of ...)| remains an error.
                 //constRequiringInitializer = false;
+#else
+                constRequiringInitializer = false;
+#endif
 
                 *forHeadKind = isForIn ? PNK_FORIN : PNK_FOROF;
             } else {
diff --git a/js/src/jit-test/tests/parser/letContextualKeyword.js b/js/src/jit-test/tests/parser/letContextualKeyword.js
index e8a1dc207..d69b4871b 100644
--- a/js/src/jit-test/tests/parser/letContextualKeyword.js
+++ b/js/src/jit-test/tests/parser/letContextualKeyword.js
@@ -18,16 +18,16 @@ eval(`let {x:x} = {x:42}; assertEq(x, 42);`);
 eval(`let [x] = [42]; assertEq(x, 42);`);
 
 eval(`for (let x in [1]) { assertEq(x, "0"); }`);
-expectError(`for (const x in [1]) { assertEq(x, "0"); }`); // XXX bug 449811
+// expectError(`for (const x in [1]) { assertEq(x, "0"); }`); // XXX bug 449811
 
 eval(`for (let x of [1]) { assertEq(x, 1); }`);
-expectError(`for (const x of [1]) { assertEq(x, 1); }`); // XXX bug 449811
+// expectError(`for (const x of [1]) { assertEq(x, 1); }`); // XXX bug 449811
 
 eval(`for (let i = 0; i < 1; i++) { assertEq(i, 0); }`);
 eval(`var done = false; for (const i = 0; !done; done = true) { assertEq(i, 0); }`);
 
 eval(`for (let of of [1]) { assertEq(of, 1); }`);
-expectError(`for (const of of [1]) { assertEq(of, 1); }`); // XXX bug 449811
+// expectError(`for (const of of [1]) { assertEq(of, 1); }`); // XXX bug 449811
 
 eval(`try { throw 17; } catch (let) { assertEq(let, 17); }`);
 eval(`try { throw [17]; } catch ([let]) { assertEq(let, 17); }`);
diff --git a/js/src/tests/ecma_6/LexicalEnvironment/const-declaration-in-for-loop.js b/js/src/tests/ecma_6/LexicalEnvironment/const-declaration-in-for-loop.js
index ba918d520..ee9c3a4e3 100644
--- a/js/src/tests/ecma_6/LexicalEnvironment/const-declaration-in-for-loop.js
+++ b/js/src/tests/ecma_6/LexicalEnvironment/const-declaration-in-for-loop.js
@@ -44,6 +44,8 @@ Function(`if (true)
               continue;
           }`)();
 
+/* Enabled by TenFourFox issue 541
+
 // We don't support for (const ... in ...) or for (const ... of ...) yet.  When
 // we do, these all should start passing without throwing a syntax error, and
 // we can remove the try/catch here, and the ultimate throw-canary forcing this
@@ -51,6 +53,8 @@ Function(`if (true)
 try
 {
 
+*/
+
 executeGlobalScript(`for (const a5 of [])
                        continue;`);
 
@@ -87,6 +91,7 @@ Function(`if (true)
               continue;
           }`)();
 
+/*
 throw new Error("Congratulations on making for (const … in/of …) work!  " +
                 "Please remove the try/catch and this throw.");
 }
@@ -95,6 +100,7 @@ catch (e)
   assertEq(e instanceof SyntaxError, true,
            "unexpected error: expected SyntaxError, got " + e);
 }
+*/
 
 /******************************************************************************/
 
diff --git a/js/src/tests/js1_8_5/reflect-parse/for-loop-destructuring.js b/js/src/tests/js1_8_5/reflect-parse/for-loop-destructuring.js
index a13571882..89dac02ee 100644
--- a/js/src/tests/js1_8_5/reflect-parse/for-loop-destructuring.js
+++ b/js/src/tests/js1_8_5/reflect-parse/for-loop-destructuring.js
@@ -26,6 +26,8 @@ assertStmt("for each ({a:x,b:y,c:z} in foo);", forEachInStmt(axbycz, ident("foo"
 assertStmt("for each (var [x,y,z] in foo);", forEachInStmt(varDecl([{ id: xyz, init: null }]), ident("foo"), emptyStmt));
 assertStmt("for each (let [x,y,z] in foo);", forEachInStmt(letDecl([{ id: xyz, init: null }]), ident("foo"), emptyStmt));
 assertStmt("for each ([x,y,z] in foo);", forEachInStmt(xyz, ident("foo"), emptyStmt));
+/*
+// Enabled by TenFourFox issue 541
 assertError("for (const x in foo);", SyntaxError);
 assertError("for (const {a:x,b:y,c:z} in foo);", SyntaxError);
 assertError("for (const [x,y,z] in foo);", SyntaxError);
@@ -35,6 +37,7 @@ assertError("for (const [x,y,z] of foo);", SyntaxError);
 assertError("for each (const x in foo);", SyntaxError);
 assertError("for each (const {a:x,b:y,c:z} in foo);", SyntaxError);
 assertError("for each (const [x,y,z] in foo);", SyntaxError);
+*/
 
 assertError("for (x = 22 in foo);", SyntaxError);-
 assertError("for ({a:x,b:y,c:z} = 22 in foo);", SyntaxError);