Index: Modules/_struct.c
===================================================================
--- Modules/_struct.c	(Revision 66049)
+++ Modules/_struct.c	(Arbeitskopie)
@@ -1779,13 +1779,16 @@
 
 	/* Extract a writable memory buffer from the first argument */
 	if ( PyObject_AsWriteBuffer(PyTuple_GET_ITEM(args, 0),
-								(void**)&buffer, &buffer_len) == -1 ) {
+				    (void**)&buffer, &buffer_len) == -1 ) {
 		return NULL;
 	}
 	assert( buffer_len >= 0 );
 
 	/* Extract the offset from the first argument */
 	offset = PyLong_AsSsize_t(PyTuple_GET_ITEM(args, 1));
+	if (offset == -1 && PyErr_Occurred()) {
+		return NULL;
+	}
 
 	/* Support negative offsets. */
 	if (offset < 0)