diff --git a/src/libs/3rdparty/cplusplus/Symbols.cpp b/src/libs/3rdparty/cplusplus/Symbols.cpp
index 9e9b66cacb8..6101e51485e 100644
--- a/src/libs/3rdparty/cplusplus/Symbols.cpp
+++ b/src/libs/3rdparty/cplusplus/Symbols.cpp
@@ -284,17 +284,32 @@ bool Function::hasReturnType() const
 
 unsigned Function::argumentCount() const
 {
-    unsigned c = memberCount();
-    if (c > 0 && memberAt(0)->type()->isVoidType())
+    const unsigned memCnt = memberCount();
+    if (memCnt > 0 && memberAt(0)->type()->isVoidType())
         return 0;
-    // Definitions with function-try-blocks will have more than a block.
-    while (c > 0 && memberAt(c - 1)->isBlock())
-        --c;
-    return c;
+
+    // Definitions with function-try-blocks will have more than a block, and
+    // arguments with a lambda as default argument will also have more blocks.
+    unsigned argc = 0;
+    for (unsigned it = 0; it < memCnt; ++it)
+        if (memberAt(it)->isArgument())
+            ++argc;
+    return argc;
 }
 
 Symbol *Function::argumentAt(unsigned index) const
-{ return memberAt(index); }
+{
+    for (unsigned it = 0, eit = memberCount(); it < eit; ++it) {
+        if (Argument *arg = memberAt(it)->asArgument()) {
+            if (index == 0)
+                return arg;
+            else
+                --index;
+        }
+    }
+
+    return 0;
+}
 
 bool Function::hasArguments() const
 {
@@ -381,7 +396,7 @@ bool Function::maybeValidPrototype(unsigned actualArgumentCount) const
     for (; minNumberArguments < argc; ++minNumberArguments) {
         Argument *arg = argumentAt(minNumberArguments)->asArgument();
 
-        if (! arg) // TODO: Fix me properly - QTCREATORBUG-8316
+        if (! arg)
             return false;
 
         if (arg->hasInitializer())
diff --git a/tests/auto/cplusplus/semantic/tst_semantic.cpp b/tests/auto/cplusplus/semantic/tst_semantic.cpp
index b8d82010e23..860a9940bcc 100644
--- a/tests/auto/cplusplus/semantic/tst_semantic.cpp
+++ b/tests/auto/cplusplus/semantic/tst_semantic.cpp
@@ -177,6 +177,7 @@ private slots:
     void q_enum_1();
 
     void lambda_1();
+    void lambda_2();
 
     void diagnostic_error();
 };
@@ -722,6 +723,33 @@ void tst_Semantic::lambda_1()
     QCOMPARE(doc->globals->memberCount(), 1U);
 }
 
+void tst_Semantic::lambda_2()
+{
+    QSharedPointer<Document> doc = document(
+                "\n"
+                "class A {\n"
+                "  void f(int i = [](){});\n"
+                "};\n"
+                , false, false, true);
+
+    QCOMPARE(doc->errorCount, 0U);
+    QCOMPARE(doc->globals->memberCount(), 1U);
+    Class *A = doc->globals->memberAt(0)->asClass();
+    QVERIFY(A);
+    QCOMPARE(A->memberCount(), 1U);
+    Declaration *d = A->memberAt(0)->asDeclaration();
+    QCOMPARE(d->name()->identifier()->chars(), "f");
+    Function *ty = d->type()->asFunctionType();
+    QVERIFY(ty);
+    QCOMPARE(ty->argumentCount(), 1U);
+    Argument *arg = ty->argumentAt(0)->asArgument();
+    QVERIFY(arg);
+    const StringLiteral *init = arg->initializer();
+    QVERIFY(init);
+    QCOMPARE(init->chars(), " [](){}");
+}
+
+
 void tst_Semantic::diagnostic_error()
 {
     QSharedPointer<Document> doc = document("\n"