diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 08524b4d9e..826da86300 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -20,6 +20,10 @@
 #include <sys/fcntl.h>
 #endif
 
+#ifndef RB_INTEGER_TYPE_P
+# define RB_INTEGER_TYPE_P(c) (FIXNUM_P(c) || RB_TYPE_P(c, T_BIGNUM))
+#endif
+
 struct StringIO {
     VALUE string;
     rb_encoding *enc;