1 files changed, 3 insertions, 0 deletions
diff --git a/ast.c b/ast.c
index 202527f53f..e1c044e24c 100644
--- a/ast.c
+++ b/ast.c
@@ -213,6 +213,9 @@ ast_s_of(rb_execution_context_t *ec, VALUE module, VALUE body, VALUE keep_script
         else {
             iseq = rb_method_iseq(body);
         }
+        if (!iseq) {
+            rb_raise(rb_eArgError, "cannot get AST for method that is not defined in Ruby");
+        }
         if (rb_iseq_from_eval_p(iseq)) {
             rb_raise(rb_eArgError, "cannot get AST for method defined in eval");
         }