diff --git a/io.c b/io.c
index 88c95a02c5..3476e1352c 100644
--- a/io.c
+++ b/io.c
@@ -167,6 +167,15 @@ rb_read_pending(fp)
     return READ_DATA_PENDING(fp);
 }
 
+void
+rb_read_check(fp)
+    FILE *fp;
+{
+    if (!READ_DATA_PENDING(fp)) {
+	rb_thread_wait_fd(fileno(fp));
+    }
+}
+
 /* writing functions */
 static VALUE
 io_write(io, str)
diff --git a/rubyio.h b/rubyio.h
index 014ca4acd7..b0d9cda3ec 100644
--- a/rubyio.h
+++ b/rubyio.h
@@ -58,5 +58,6 @@ void rb_io_synchronized _((OpenFile*));
 void rb_io_check_closed _((OpenFile*));
 void rb_eof_error _((void));
 
+void rb_read_check _((FILE*));
 int rb_read_pending _((FILE*));
 #endif