1 files changed, 3 insertions, 0 deletions
diff --git a/eval.c b/eval.c
index 178ff62137..4c6e8e98b4 100644
--- a/eval.c
+++ b/eval.c
@@ -457,6 +457,9 @@ exc_setup_cause(VALUE exc, VALUE cause)
 #endif
     if (!NIL_P(cause) && cause != exc) {
 	rb_ivar_set(exc, id_cause, cause);
+	if (!rb_ivar_defined(cause, id_cause)) {
+	    rb_ivar_set(cause, id_cause, Qnil);
+	}
     }
     return exc;
 }