diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index a7558255a5..6bb8701aa9 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -844,7 +844,7 @@ pg_plan_queries(List *querytrees, int cursorOptions, ParamListInfo boundParams)
 
 	foreach(query_list, querytrees)
 	{
-		Query	   *query = (Query *) lfirst(query_list);
+		Query	   *query = castNode(Query, lfirst(query_list));
 		Node	   *stmt;
 
 		if (query->commandType == CMD_UTILITY)
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 6b850e4bc4..f7fd8ec6be 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -542,6 +542,26 @@ extern PGDLLIMPORT Node *newNodeMacroHolder;
 
 #define IsA(nodeptr,_type_)		(nodeTag(nodeptr) == T_##_type_)
 
+/*
+ * castNode(type, ptr) casts ptr to type and, if cassert is enabled, verifies
+ * that the the c actually has the appropriate type (using it's nodeTag()).
+ *
+ * Use an inline function when assertions are enabled, to avoid multiple
+ * evaluations of the ptr argument (which could e.g. be a function call).
+ */
+#ifdef USE_ASSERT_CHECKING
+static inline Node*
+castNodeImpl(enum NodeTag type, void *ptr)
+{
+	Assert(ptr == NULL || nodeTag(ptr) == type);
+	return ptr;
+}
+#define castNode(_type_, nodeptr) ((_type_ *) castNodeImpl(T_##_type_, nodeptr))
+#else
+#define castNode(_type_,nodeptr)  ((_type_ *)(nodeptr))
+#endif
+
+
 /* ----------------------------------------------------------------
  *					  extern declarations follow
  * ----------------------------------------------------------------