diff --git a/contracts/eosiolib/crypto.h b/contracts/eosiolib/crypto.h
index efa9a7b54d64a43524fad0d463a7c38206037b93..cae78328e151fbd5ed2d33ec7f39cf0b08e71503 100644
--- a/contracts/eosiolib/crypto.h
+++ b/contracts/eosiolib/crypto.h
@@ -78,12 +78,12 @@ void ripemd160( char* data, uint32_t length, checksum160* hash );
  * returns the number of bytes read into pub
  * `digest` should be checksum<256>
  */
-int recover_key( checksum256* digest, const char* sig, size_t siglen, char* pub, size_t publen );
+int recover_key( const checksum256* digest, const char* sig, size_t siglen, char* pub, size_t publen );
 
 /**
  * Tests a given public key with the generated key from digest and the signature
  * `digest` should be checksum<256>
  */
-void assert_recover_key( checksum256* digest, const char* sig, size_t siglen, const char* pub, size_t publen );
+void assert_recover_key( const checksum256* digest, const char* sig, size_t siglen, const char* pub, size_t publen );
 
 }