diff --git a/src/v_draw.cpp b/src/v_draw.cpp
index 6d86e0a0eb..6430b9448f 100644
--- a/src/v_draw.cpp
+++ b/src/v_draw.cpp
@@ -198,6 +198,8 @@ void DCanvas::DrawTextureParms(FTexture *img, DrawParms &parms)
 	
 	viewport->RenderTarget = screen;
 
+	viewport->RenderTarget->Lock(true);
+
 	if (APART(parms.colorOverlay) != 0)
 	{
 		// The software renderer cannot invert the source without inverting the overlay
@@ -324,6 +326,8 @@ void DCanvas::DrawTextureParms(FTexture *img, DrawParms &parms)
 	{
 		NetUpdate();
 	}
+
+	viewport->RenderTarget->Unlock();
 #endif
 }