diff --git a/src/convert-dg-to-py.cc b/src/convert-dg-to-py.cc
index 542b67084e4bc20a4b9892fc0f09edd9980aedaa..92461e76f3669b3b11cc69703bc91a931035c3a5 100644
--- a/src/convert-dg-to-py.cc
+++ b/src/convert-dg-to-py.cc
@@ -171,7 +171,7 @@ namespace dynamicgraph {
 	      throw ExceptionPython(ExceptionPython::MATRIX_PARSING,
 				     "matrix");
 	    }
-	    fillMatrixRow(m, iRow, row);
+	    fillMatrixRow(m, static_cast<unsigned> (iRow), row);
 	  }
 	  return Value(m);
 	  break;