1 files changed, 5 insertions, 1 deletions

diff --git a/hash.c b/hash.c
index 209fe26c37..89666ca831 100644
--- a/hash.c
+++ b/hash.c
@@ -131,9 +131,13 @@ rb_hash_foreach_iter(key, value, arg)
 
     if (key == Qundef) return ST_CONTINUE;
     status = (*arg->func)(key, value, arg->arg);
-    if (RHASH(arg->hash)->tbl != tbl || RHASH(arg->hash)->tbl->bins != bins){
+    if (RHASH(arg->hash)->tbl != tbl ||
+	RHASH(arg->hash)->tbl->bins != bins) {
 	rb_raise(rb_eIndexError, "rehash occurred during iteration");
     }
+    if (RHASH(arg->hash)->iter_lev == 0) {
+	rb_raise(rb_eArgError, "block re-entered");
+    }
     return status;
 }