diff --git a/src/include/libpq/crypt.h b/src/include/libpq/crypt.h
index 7c01c8297b..35e65ed642 100644
--- a/src/include/libpq/crypt.h
+++ b/src/include/libpq/crypt.h
@@ -13,7 +13,7 @@
 
 #define CRYPT_PWD_FILE	"pg_pwd"
 
-extern char* crypt_getpwdfilename();
+extern char* crypt_getpwdfilename(void);
 extern MsgType crypt_salt(const char* user);
 extern int crypt_verify(Port* port, const char* user, const char* pgpass);