diff --git a/dom/bindings/parser/WebIDL.py b/dom/bindings/parser/WebIDL.py
index 9adc1c781e40..33537378d378 100644
--- a/dom/bindings/parser/WebIDL.py
+++ b/dom/bindings/parser/WebIDL.py
@@ -2962,7 +2962,6 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
         for overload in self._overloads:
             inOptionalArguments = False
             variadicArgument = None
-            sawOptionalWithNoDefault = False
 
             arguments = overload.arguments
             for (idx, argument) in enumerate(arguments):
@@ -3003,18 +3002,9 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
                     raise WebIDLError("Non-optional argument after optional "
                                       "arguments",
                                       [argument.location])
-                # Once we see an argument with no default value, there can
-                # be no more default values.
-                if sawOptionalWithNoDefault and argument.defaultValue:
-                    raise WebIDLError("Argument with default value after "
-                                      "optional arguments with no default "
-                                      "values",
-                                      [argument.location])
                 inOptionalArguments = argument.optional
                 if argument.variadic:
                     variadicArgument = argument
-                sawOptionalWithNoDefault = (argument.optional and
-                                            not argument.defaultValue)
 
             returnType = overload.returnType
             if returnType.isComplete():
diff --git a/dom/bindings/parser/tests/test_optional_constraints.py b/dom/bindings/parser/tests/test_optional_constraints.py
index 1dcdc7fb8a51..99fd07fe93f8 100644
--- a/dom/bindings/parser/tests/test_optional_constraints.py
+++ b/dom/bindings/parser/tests/test_optional_constraints.py
@@ -11,4 +11,20 @@ def WebIDLTest(parser, harness):
     except:
         threw = True
 
-    harness.ok(threw, "Should have thrown.")
+    harness.ok(threw,
+               "Should have thrown on non-optional argument following optional "
+               "argument.")
+
+    parser = parser.reset()
+    parser.parse("""
+        interface OptionalConstraints2 {
+          void foo(optional byte arg1 = 1, optional byte arg2 = 2,
+                   optional byte arg3, optional byte arg4 = 4,
+                   optional byte arg5, optional byte arg6 = 9);
+        };
+    """)
+    results = parser.finish()
+    args = results[0].members[0].signatures()[0][1]
+    harness.check(len(args), 6, "Should have 6 arguments")
+    harness.check(args[5].defaultValue.value, 9,
+                  "Should have correct default value")
diff --git a/dom/bindings/test/TestBindingHeader.h b/dom/bindings/test/TestBindingHeader.h
index 94410d079ba3..9872c62a8236 100644
--- a/dom/bindings/test/TestBindingHeader.h
+++ b/dom/bindings/test/TestBindingHeader.h
@@ -610,6 +610,9 @@ public:
   bool ThrowingSetterAttr() const;
   void SetThrowingSetterAttr(bool arg, ErrorResult& aRv);
   int16_t LegacyCall(JS::Value, uint32_t, TestInterface&);
+  void PassArgsWithDefaults(JSContext*, const Optional<int32_t>&,
+                            TestInterface*, const Dict&, double,
+                            const Optional<float>&);
 
   // Methods and properties imported via "implements"
   bool ImplementedProperty();
diff --git a/dom/bindings/test/TestCodeGen.webidl b/dom/bindings/test/TestCodeGen.webidl
index 3d66ac638942..c98a00dccb01 100644
--- a/dom/bindings/test/TestCodeGen.webidl
+++ b/dom/bindings/test/TestCodeGen.webidl
@@ -583,6 +583,10 @@ interface TestInterface {
   [GetterThrows] attribute boolean throwingGetterAttr;
   [SetterThrows] attribute boolean throwingSetterAttr;
   legacycaller short(unsigned long arg1, TestInterface arg2);
+  void passArgsWithDefaults(optional long arg1,
+                            optional TestInterface? arg2 = null,
+                            optional Dict arg3, optional double arg4 = 5.0,
+                            optional float arg5);
 
   // If you add things here, add them to TestExampleGen and TestJSImplGen as well
 };
diff --git a/dom/bindings/test/TestExampleGen.webidl b/dom/bindings/test/TestExampleGen.webidl
index 3174440dc1dd..499ddd5ec356 100644
--- a/dom/bindings/test/TestExampleGen.webidl
+++ b/dom/bindings/test/TestExampleGen.webidl
@@ -480,6 +480,10 @@ interface TestExampleInterface {
   [GetterThrows] attribute boolean throwingGetterAttr;
   [SetterThrows] attribute boolean throwingSetterAttr;
   legacycaller short(unsigned long arg1, TestInterface arg2);
+  void passArgsWithDefaults(optional long arg1,
+                            optional TestInterface? arg2 = null,
+                            optional Dict arg3, optional double arg4 = 5.0,
+                            optional float arg5);
 
   // If you add things here, add them to TestCodeGen and TestJSImplGen as well
 };
diff --git a/dom/bindings/test/TestJSImplGen.webidl b/dom/bindings/test/TestJSImplGen.webidl
index 1b575c38ad6f..a933af2d37fe 100644
--- a/dom/bindings/test/TestJSImplGen.webidl
+++ b/dom/bindings/test/TestJSImplGen.webidl
@@ -470,6 +470,11 @@ interface TestJSImplInterface {
   [Throws] attribute boolean throwingAttr;
   [GetterThrows] attribute boolean throwingGetterAttr;
   [SetterThrows] attribute boolean throwingSetterAttr;
+  // legacycaller short(unsigned long arg1, TestInterface arg2);
+  void passArgsWithDefaults(optional long arg1,
+                            optional TestInterface? arg2 = null,
+                            optional Dict arg3, optional double arg4 = 5.0,
+                            optional float arg5);
 
   // If you add things here, add them to TestCodeGen as well
 };