diff --git a/m-tool.cc b/m-tool.cc
index 9446270..9c9bbbe 100644
--- a/m-tool.cc
+++ b/m-tool.cc
@@ -175,14 +175,23 @@ void T_Main::makeUI( )
 void T_Main::render( )
 {
 	if ( demo ) {
-		demo->render( );
+		const bool hadReset = demo->render( );
+		if ( hadReset ) {
+			UI::Profiler( ).clear( );
+			UI::Profiler( ).startFrame( );
+			UI::Profiler( ).start( "Full frame" );
+		}
 
-		UI::Profiler( ).start( "Debug" );
+		if ( !hadReset ) {
+			UI::Profiler( ).start( "Debug" );
+		}
 		T_Rendertarget::MainOutput( );
 		if ( UI::ODbg( ).isActive( ) ) {
 			UI::ODbg( ).debugOutput( );
 		}
-		UI::Profiler( ).end( "Debug" );
+		if ( !hadReset ) {
+			UI::Profiler( ).end( "Debug" );
+		}
 
 	} else {
 		T_Rendertarget::MainOutput( );
diff --git a/ui-demo.cc b/ui-demo.cc
index cfdcb5f..d18cbef 100644
--- a/ui-demo.cc
+++ b/ui-demo.cc
@@ -23,12 +23,14 @@ bool T_Demo::initialise(
 	return program && runInit( *program );
 }
 
-void T_Demo::render( )
+bool T_Demo::render( )
 {
+	bool rv = false;
 	if ( Common::Ops( ).hasNewProgram( ) ) {
 		auto nProgram{ Common::Ops( ).program( ) };
 		if ( runInit( *nProgram ) ) {
 			program = std::move( nProgram );
+			rv = true;
 		}
 	}
 
@@ -44,6 +46,7 @@ void T_Demo::render( )
 			context->aborted = true;
 		}
 	}
+	return rv;
 }
 
 bool T_Demo::runInit(
diff --git a/ui-demo.hh b/ui-demo.hh
index e3ced13..76d766e 100644
--- a/ui-demo.hh
+++ b/ui-demo.hh
@@ -16,7 +16,7 @@ struct T_Demo
 
 	bool initialise( const uint32_t width ,
 			const uint32_t height );
-	void render( );
+	bool render( );
 
 	// ---------------------------------------------------------------------
 
diff --git a/ui-profiling.cc b/ui-profiling.cc
index a937bcc..73a8ab1 100644
--- a/ui-profiling.cc
+++ b/ui-profiling.cc
@@ -94,6 +94,7 @@ void T_Profiler::start(
 		parents_.add( Invalid );
 	}
 
+	assert( previous_ == Invalid || previous_ < pos );
 	chain_[ pos ] = previous_;
 	if ( current_ != Invalid ) {
 		parents_[ pos ] = current_;