diff --git a/lib/CalypPythonModuleIf.cpp b/lib/CalypPythonModuleIf.cpp
index e2cb5ff..8b096f5 100644
--- a/lib/CalypPythonModuleIf.cpp
+++ b/lib/CalypPythonModuleIf.cpp
@@ -464,7 +464,7 @@ CalypFrame* CalypPythonModuleIf::process( std::vector<CalypFrame*> apcFrameList
     PyObject* pyInputArg = PyTuple_New( apcFrameList.size() );
     for( unsigned i = 0; i < apcFrameList.size(); i++ )
     {
-      apcFrameList[0]->toMat( cvMatInput[0], m_bConvertToGray, false );
+      apcFrameList[0]->toMat( cvMatInput[i], m_bConvertToGray, false );
 
       PyObject* pyMat = pyopencv_from( cvMatInput[i] );
       /* pValue reference stolen here: */