diff --git a/include/extern.h b/include/extern.h
index 81669993f..0ca8d4d3c 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -183,7 +183,7 @@ E void HostServSyncVhosts(NickAlias *na);
 /**** encrypt.c ****/
 E int enc_encrypt(const std::string &src, std::string &dest);
 E int enc_encrypt_in_place(std::string &buf);
-E int enc_decrypt(std::string &src, std::string &dest);
+E int enc_decrypt(const std::string &src, std::string &dest);
 E int enc_check_password(std::string &plaintext, std::string &password);
 
 /**** hostserv.c  ****/
diff --git a/src/encrypt.c b/src/encrypt.c
index 628079297..29a63e54e 100644
--- a/src/encrypt.c
+++ b/src/encrypt.c
@@ -50,7 +50,7 @@ int enc_encrypt_in_place(std::string &buf)
  * allow decryption, and -1 if another failure occurred (e.g. destination
  * buffer too small).
  **/
-int enc_decrypt(std::string &src, std::string &dest)
+int enc_decrypt(const std::string &src, std::string &dest)
 {
 	size_t pos = src.find(":");
 	if (pos == std::string::npos)