diff --git a/lib/chibi/bytevector.scm b/lib/chibi/bytevector.scm
index 4b6041a1..e2cd8e73 100644
--- a/lib/chibi/bytevector.scm
+++ b/lib/chibi/bytevector.scm
@@ -49,6 +49,12 @@
               (+ (arithmetic-shift n 8)
                  (bytevector-u8-ref bv i)))))))
 
+(define (bytevector-pad-left bv len)
+  (let ((diff (- len (bytevector-length bv))))
+    (if (positive? diff)
+        (bytevector-append bv (make-bytevector diff 0))
+        bv)))
+
 ;;> \section{Hex string conversion}
 
 ;;> Big-endian conversion, guaranteed padded to even length.
diff --git a/lib/chibi/bytevector.sld b/lib/chibi/bytevector.sld
index 42b83a86..1923cc02 100644
--- a/lib/chibi/bytevector.sld
+++ b/lib/chibi/bytevector.sld
@@ -3,8 +3,9 @@
   (export
    bytevector-u16-ref-le bytevector-u16-ref-be
    bytevector-u32-ref-le bytevector-u32-ref-be
+   bytevector-pad-left
    integer->bytevector bytevector->integer
    integer->hex-string hex-string->integer
    bytevector->hex-string hex-string->bytevector)
-  (import (chibi) (srfi 33))
+  (import (scheme base) (srfi 33))
   (include "bytevector.scm"))