1 files changed, 4 insertions, 0 deletions
diff --git a/io.c b/io.c
index a3dfa027d4..a023039209 100644
--- a/io.c
+++ b/io.c
@@ -12125,9 +12125,13 @@ static VALUE
 rb_io_s_read(int argc, VALUE *argv, VALUE io)
 {
     VALUE opt, offset;
+    long off;
     struct foreach_arg arg;
 
     argc = rb_scan_args(argc, argv, "13:", NULL, NULL, &offset, NULL, &opt);
+    if (!NIL_P(offset) && (off = NUM2LONG(offset)) < 0) {
+        rb_raise(rb_eArgError, "negative offset %ld given", off);
+    }
     open_key_args(io, argc, argv, opt, &arg);
     if (NIL_P(arg.io)) return Qnil;
     if (!NIL_P(offset)) {