diff --git a/iseq.c b/iseq.c
index 20c5fff2f2..831a9e8109 100644
--- a/iseq.c
+++ b/iseq.c
@@ -1075,9 +1075,14 @@ iseqw_s_compile(int argc, VALUE *argv, VALUE self)
       case 3: path = argv[--i];
       case 2: file = argv[--i];
     }
+
     if (NIL_P(file)) file = rb_fstring_cstr("<compiled>");
+    if (NIL_P(path)) path = file;
     if (NIL_P(line)) line = INT2FIX(1);
 
+    Check_Type(path, T_STRING);
+    Check_Type(file, T_STRING);
+
     return iseqw_new(rb_iseq_compile_with_option(src, file, path, line, 0, opt));
 }