diff --git a/effects/backgroundcontrast/contrast.cpp b/effects/backgroundcontrast/contrast.cpp
--- a/effects/backgroundcontrast/contrast.cpp
+++ b/effects/backgroundcontrast/contrast.cpp
@@ -483,6 +483,7 @@
 
     // Upload geometry for the horizontal and vertical passes
     GLVertexBuffer *vbo = GLVertexBuffer::streamingBuffer();
+    vbo->reset();
     uploadGeometry(vbo, actualShape);
     vbo->bindArrays();