diff --git a/crypto/bn/bn_lcl.h b/crypto/bn/bn_lcl.h
index 39ad05631a1b60696b4ba28f447fa3a41209a19f..a14188e2d207c51bedee0ef8ec89cfe370d086fa 100644
--- a/crypto/bn/bn_lcl.h
+++ b/crypto/bn/bn_lcl.h
@@ -414,6 +414,8 @@ void bn_mul_low_recursive(BN_ULONG *r,BN_ULONG *a,BN_ULONG *b,int n2,
 	BN_ULONG *t);
 void bn_mul_high(BN_ULONG *r,BN_ULONG *a,BN_ULONG *b,BN_ULONG *l,int n2,
 	BN_ULONG *t);
+BN_ULONG bn_sub_part_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b,
+	int cl, int dl);
 
 #ifdef  __cplusplus
 }