diff --git a/src/generator.h b/src/generator.h
index 9d0b571..a3f7620 100644
--- a/src/generator.h
+++ b/src/generator.h
@@ -267,7 +267,7 @@ private:
 	// as std::wostringstream are not copyable
 	std::vector<StreamType*> filter_tab;
 	std::vector<StreamType*> ezc_frame_stack_tab;
-	const StreamType empty_stream;
+	StreamType empty_stream;
 
 	// temporary streams used in [if..] [for...] or [def ...]
 	// or if output_stream is null and an ezc function should be called
@@ -391,7 +391,7 @@ private:
 	bool Call(Item::Function & item_fun,
 			  const std::wstring * fun_name,
 			  Var<StreamType> & result,
-			  const StreamType & in_stream);
+			  StreamType & in_stream);
 
 	bool Call(Item::Function & item_fun, Var<StreamType> & result);
 
@@ -2083,7 +2083,7 @@ bool Generator<StreamType, is_pikotools_stream, is_autoescape_stream>::Call(
 		Item::Function & item_fun,
 		const std::wstring * fun_name,
 		Var<StreamType> & result,
-		const StreamType & in_stream)
+		StreamType & in_stream)
 {
 //FindHelperOld find_helper;
 std::vector<Var<StreamType>> parameters;
@@ -2124,6 +2124,7 @@ std::vector<Var<StreamType>> parameters;
 
 		if( fun_child.is_function )
 		{
+			empty_stream.clear();
 			Call(fun_child, nullptr, parameters[i], empty_stream);
 		}
 		else
@@ -2134,6 +2135,8 @@ std::vector<Var<StreamType>> parameters;
 	}
 
 	Var<StreamType> empty_input; // fix me for filters
+	empty_input.type = Var<StreamType>::TYPE_STREAM;
+	empty_input.stream = in_stream; // IMPROVEME don't copy here streams, let Var::stream be a pointer?
 
 	FindHelper find_helper(*name, item_fun.fields, parameters);
 	find_helper.result = &result;
@@ -2150,6 +2153,7 @@ template<class StreamType, bool is_pikotools_stream, bool is_autoescape_stream>
 bool Generator<StreamType, is_pikotools_stream, is_autoescape_stream>::Call(Item::Function & item_fun, Var<StreamType> & result)
 {
 	//return Call(item_fun, nullptr, stream_temp1, true, result, empty_stream);
+	empty_stream.clear();
 	return Call(item_fun, nullptr, result, empty_stream);
 }
 
@@ -2533,6 +2537,7 @@ void Generator<StreamType, is_pikotools_stream, is_autoescape_stream>::MakeTextF
 	else
 	{
 		Var<StreamType> result;
+		empty_stream.clear();
 
 		if( Call(item.function, nullptr, result, empty_stream) )
 		{
@@ -2666,6 +2671,7 @@ void Generator<StreamType, is_pikotools_stream, is_autoescape_stream>::MakeTextF
 		else
 		{
 			//Call(item.function, nullptr, stream_temp1, true, result, empty_stream);
+			empty_stream.clear();
 			Call(item.function, nullptr, result, empty_stream);
 		}
 
@@ -2703,6 +2709,7 @@ void Generator<StreamType, is_pikotools_stream, is_autoescape_stream>::MakeTextD
 	{
 		// call function
 		//if( Call(fun, nullptr, stream_temp_define, true, var, empty_stream) )
+		empty_stream.clear();
 		if( Call(fun, nullptr, var, empty_stream) )
 		{
 			//CopyStreamToString(stream_temp_define, var.str);
@@ -2975,6 +2982,7 @@ void Generator<StreamType, is_pikotools_stream, is_autoescape_stream>::MakeTextR
 		// this Call() sets last_res which is used later when we return to CallBlock()
 		//Call(item.function, nullptr, stream_temp1, false, result, empty_stream);
 		//ClearStream(stream_temp1);
+		empty_stream.clear();
 		Call(item.function, nullptr, result, empty_stream);
 	}
 }