diff --git a/src/App/DocumentObjectPyImp.cpp b/src/App/DocumentObjectPyImp.cpp
index 6dda3c9d16..da62d024d2 100644
--- a/src/App/DocumentObjectPyImp.cpp
+++ b/src/App/DocumentObjectPyImp.cpp
@@ -285,10 +285,10 @@ PyObject*  DocumentObjectPy::setExpression(PyObject * args)
         PyObject* unicode = PyUnicode_AsEncodedString(expr, "utf-8", 0);
         if (unicode) {
             std::string exprStr = PyString_AsString(unicode);
+            Py_DECREF(unicode);
             boost::shared_ptr<Expression> shared_expr(ExpressionParser::parse(getDocumentObjectPtr(), exprStr.c_str()));
 
             getDocumentObjectPtr()->setExpression(p, shared_expr, comment);
-            Py_DECREF(unicode);
         }
         else {
             // utf-8 encoding failed
diff --git a/src/App/DocumentPyImp.cpp b/src/App/DocumentPyImp.cpp
index d69f4e6958..ce7bda4983 100644
--- a/src/App/DocumentPyImp.cpp
+++ b/src/App/DocumentPyImp.cpp
@@ -346,9 +346,12 @@ PyObject*  DocumentPy::openTransaction(PyObject *args)
         cmd = PyString_AsString(value);
     }
 #endif
-    else
+    else {
+        PyErr_SetString(PyExc_TypeError, "string or unicode expected");
         return NULL;
-    getDocumentPtr()->openTransaction(cmd.c_str()); 
+    }
+
+    getDocumentPtr()->openTransaction(cmd.c_str());
     Py_Return; 
 }