1 files changed, 8 insertions, 2 deletions
diff --git a/enum.c b/enum.c
index 2a29272ae9..de2278c333 100644
--- a/enum.c
+++ b/enum.c
@@ -391,12 +391,17 @@ sort_by_i(i, ary)
 }
 
 static int
-sort_by_cmp(aa, bb)
+sort_by_cmp(aa, bb, data)
     NODE **aa, **bb;
+    void *data;
 {
     VALUE a = aa[0]->u1.value;
     VALUE b = bb[0]->u1.value;
+    VALUE ary = (VALUE)data;
 
+    if (RBASIC(ary)->klass) {
+	rb_raise(rb_eRuntimeError, "sort_by reentered");
+    }
     return rb_cmpint(rb_funcall(a, id_cmp, 1, b), a, b);
 }
 
@@ -485,7 +490,8 @@ enum_sort_by(obj)
     RBASIC(ary)->klass = 0;
     rb_iterate(rb_each, obj, sort_by_i, ary);
     if (RARRAY(ary)->len > 1) {
-	qsort(RARRAY(ary)->ptr, RARRAY(ary)->len, sizeof(VALUE), sort_by_cmp, 0);
+	qsort(RARRAY(ary)->ptr, RARRAY(ary)->len, sizeof(VALUE),
+	      sort_by_cmp, (void *)ary);
     }
     if (RBASIC(ary)->klass) {
 	rb_raise(rb_eRuntimeError, "sort_by reentered");