diff --git a/lib/scheme/extras.scm b/lib/scheme/extras.scm
index b87ce396..9796a0e1 100644
--- a/lib/scheme/extras.scm
+++ b/lib/scheme/extras.scm
@@ -135,9 +135,11 @@
   (if (zero? n)
       #u8()
       (let ((in (if (pair? o) (car o) (current-input-port)))
-            (res (make-bytevector n)))
-        (read-bytevector! res in)
-        res)))
+            (vec (make-bytevector n))
+            (res (read-bytevector! vec in)))
+        (cond ((eof-object? res) res)
+              ((< res n) (subbytes vec 0 i))
+              (else res)))))
 
 (define (read-bytevector! vec . o)
   (let* ((in (if (pair? o) (car o) (current-input-port)))