diff --git a/dlls/crypt32/crypt32_private.h b/dlls/crypt32/crypt32_private.h
index e29249b1136..d61fcfb7d6e 100644
--- a/dlls/crypt32/crypt32_private.h
+++ b/dlls/crypt32/crypt32_private.h
@@ -46,7 +46,7 @@ BOOL CNG_ImportPubKey(CERT_PUBLIC_KEY_INFO *pubKeyInfo, BCRYPT_KEY_HANDLE *key)
 /* Copies `len` bytes from `src` to `dst`,
  * reversing the order of the bytes
  */
-void CRYPT_CopyReversed(BYTE *dst, const BYTE *src, size_t len);
+void CRYPT_CopyReversed(BYTE *dst, const BYTE *src, size_t len) DECLSPEC_HIDDEN;
 
 BOOL CRYPT_EncodeLen(DWORD len, BYTE *pbEncoded, DWORD *pcbEncoded) DECLSPEC_HIDDEN;