diff --git a/bitpack.h b/bitpack.h
index 8e6b023..e67664e 100644
--- a/bitpack.h
+++ b/bitpack.h
@@ -227,6 +227,7 @@ unsigned char *_bitd1unpack128h32(const unsigned char *__restrict in, unsigned n
 unsigned char *_bitunpack256v32(  const unsigned char *__restrict in, unsigned n, unsigned *__restrict out, unsigned b, unsigned *__restrict pex, unsigned char *bb);
 unsigned char *_bitdunpack256v32( const unsigned char *__restrict in, unsigned n, unsigned *__restrict out, unsigned start, unsigned b, unsigned *__restrict pex, unsigned char *bb);
 unsigned char *_bitd1unpack256v32(const unsigned char *__restrict in, unsigned n, unsigned *__restrict out, unsigned start, unsigned b, unsigned *__restrict pex, unsigned char *bb);
+unsigned char *_bitzunpack256v32( const unsigned char *__restrict in, unsigned n, unsigned *__restrict out, unsigned start, unsigned b, unsigned *__restrict pex, unsigned char *bb);
 #ifdef __cplusplus
 }
 #endif