diff --git a/source/modules/FrameDifference.cpp b/source/modules/FrameDifference.cpp
index 87d89d5..3b7b1c4 100644
--- a/source/modules/FrameDifference.cpp
+++ b/source/modules/FrameDifference.cpp
@@ -54,7 +54,7 @@ Void FrameDifference::create( PlaYUVerFrame* Input )
 PlaYUVerFrame* FrameDifference::process( PlaYUVerFrame* Input1, PlaYUVerFrame* Input2 )
 {
   Pel* pInput1PelYUV = Input1->getPelBufferYUV()[0][0];
-  Pel* pInput2PelYUV = Input1->getPelBufferYUV()[0][0];
+  Pel* pInput2PelYUV = Input2->getPelBufferYUV()[0][0];
   Pel* pOutputPelYUV = m_pcFrameDifference->getPelBufferYUV()[0][0];
 
   for( UInt y = 0; y < m_pcFrameDifference->getHeight(); y++ )
diff --git a/source/modules/FrameDifference.h b/source/modules/FrameDifference.h
index ae17e3d..a3447b7 100644
--- a/source/modules/FrameDifference.h
+++ b/source/modules/FrameDifference.h
@@ -49,7 +49,7 @@ public:
   {
   }
   Void create( PlaYUVerFrame* Input );
-  PlaYUVerFrame* process( PlaYUVerFrame* Input1, PlaYUVerFrame* Input2=NULL );
+  PlaYUVerFrame* process( PlaYUVerFrame* Input1, PlaYUVerFrame* Input2 );
   Void destroy();
 
 };