diff --git a/completion/helpers.cpp b/completion/helpers.cpp
--- a/completion/helpers.cpp
+++ b/completion/helpers.cpp
@@ -131,7 +131,10 @@
 
 
             if (num >= firstDefaultParam) {
-                ret += " = " + decl->defaultParameters()[defaultParamNum].str();
+                IndexedString defaultStr = decl->defaultParameters()[defaultParamNum];
+                if (!defaultStr.isEmpty()) {
+                    ret += " = " + defaultStr.str();
+                }
                 ++defaultParamNum;
             }
 
diff --git a/duchain/builders/declarationbuilder.cpp b/duchain/builders/declarationbuilder.cpp
--- a/duchain/builders/declarationbuilder.cpp
+++ b/duchain/builders/declarationbuilder.cpp
@@ -761,8 +761,8 @@
         } else if ( node->parameterType && node->parameterType->objectType && symbol.compare(QLatin1String("null"), Qt::CaseInsensitive) != 0 ) {
             reportError(i18n("Default value for parameters with a class type hint can only be NULL."), node->defaultValue);
         }
-    } else if ( !node->defaultValue && funDec->defaultParametersSize() ) {
-        reportError(i18n("Following parameters must have a default value assigned."), node);
+    } else {
+        funDec->addDefaultParameter(IndexedString{});
     }
     {
         // create variable declaration for argument
diff --git a/duchain/navigation/declarationnavigationcontext.cpp b/duchain/navigation/declarationnavigationcontext.cpp
--- a/duchain/navigation/declarationnavigationcontext.cpp
+++ b/duchain/navigation/declarationnavigationcontext.cpp
@@ -216,8 +216,12 @@
           modifyHtml() += ' ' + identifierHighlight(decls[currentArgNum]->identifier().toString().toHtmlEscaped(), declaration());
         }
 
-        if( currentArgNum >= firstDefaultParam )
-          modifyHtml() += " = " + function->defaultParameters()[ currentArgNum - firstDefaultParam ].str().toHtmlEscaped();
+        if (currentArgNum >= firstDefaultParam) {
+          IndexedString defaultStr = function->defaultParameters()[currentArgNum - firstDefaultParam];
+          if (!defaultStr.isEmpty()) {
+            modifyHtml() += " = " + defaultStr.str().toHtmlEscaped();
+          }
+        }
       }
 
       ++currentArgNum;
diff --git a/duchain/tests/duchain.cpp b/duchain/tests/duchain.cpp
--- a/duchain/tests/duchain.cpp
+++ b/duchain/tests/duchain.cpp
@@ -1354,9 +1354,10 @@
     AbstractFunctionDeclaration* fun = dynamic_cast<AbstractFunctionDeclaration*>(top->localDeclarations().first());
     QVERIFY(fun);
 
-    QCOMPARE(fun->defaultParametersSize(), 2u);
-    QCOMPARE(fun->defaultParameters()[0].str(), QString("false"));
-    QCOMPARE(fun->defaultParameters()[1].str(), QString("null"));
+    QCOMPARE(fun->defaultParametersSize(), 3u);
+    QVERIFY(fun->defaultParameters()[0].isEmpty());
+    QCOMPARE(fun->defaultParameters()[1].str(), QString("false"));
+    QCOMPARE(fun->defaultParameters()[2].str(), QString("null"));
 }
 
 void TestDUChain::defaultFunctionParamWithTypehint() {