diff --git a/cmd/slang/main.go b/cmd/slang/main.go
index 4efe2a45..1523c601 100644
--- a/cmd/slang/main.go
+++ b/cmd/slang/main.go
@@ -148,6 +148,14 @@ func runHttpPost(operator *core.Operator, bind string) {
 
 		})
 
+	// In order to generate a response to a HTTP-Request we need to have
+	// the out port fully connected. In some cases the out port is a map of multiple
+	// types and we need them all connected to their `src`. Otherwise we `pull` on the port
+	// and wait forever to return something. Which would make the client timeout.
+	if err := operator.Main().Out().FullyConnected(); err != nil {
+		log.Fatal(err)
+	}
+
 	operator.Main().Out().Bufferize()
 	operator.Start()
 	log.Print("started as httpPost")
diff --git a/pkg/core/port.go b/pkg/core/port.go
index c0669eba..babd15be 100644
--- a/pkg/core/port.go
+++ b/pkg/core/port.go
@@ -740,6 +740,29 @@ func (p *Port) Bufferize() {
 	}
 }
 
+// Check port has a `src`
+// What is strange though for an operator with a connected delegate this would
+// return an error. For instance if you take `controlIterate` and connect the delegate.
+// And nothing more it would still work when you `push` and `pull` on `controlIterateId`
+func (p *Port) FullyConnected() error {
+	if p.PrimitiveType() {
+		if p.src == nil && p.strSrc.src == nil {
+			return fmt.Errorf("%v is not connected to a source", p.Name())
+		} else {
+			return nil
+		}
+	} else if p.itemType == TYPE_MAP {
+		for _, sub := range p.subs {
+			if err := sub.FullyConnected(); err != nil {
+				return err
+			}
+		}
+	} else if p.itemType == TYPE_STREAM {
+		return p.sub.FullyConnected()
+	}
+	return nil
+}
+
 // PRIVATE METHODS
 
 func setParentStreams(p *Port, parent *Port) {
diff --git a/pkg/elem/control_iterate_test.go b/pkg/elem/control_iterate_test.go
index 877f0a89..47146345 100644
--- a/pkg/elem/control_iterate_test.go
+++ b/pkg/elem/control_iterate_test.go
@@ -132,6 +132,7 @@ func Test_CtrlIterate__SimpleAggregation(t *testing.T) {
 	// Connect
 	require.NoError(t, ao.Delegate("iterator").Out().Connect(fo.Main().In()))
 	require.NoError(t, fo.Main().Out().Connect(ao.Delegate("iterator").In()))
+	require.NoError(t, ao.Main().Out().FullyConnected())
 
 	ao.Main().Out().Bufferize()