diff --git a/include/libssh2.h b/include/libssh2.h
index b3c51f9d..5e68cdbf 100644
--- a/include/libssh2.h
+++ b/include/libssh2.h
@@ -220,6 +220,8 @@ typedef struct _LIBSSH2_LISTENER					LIBSSH2_LISTENER;
 #define LIBSSH2_ERROR_SOCKET_TIMEOUT			-30
 #define LIBSSH2_ERROR_SFTP_PROTOCOL				-31
 #define LIBSSH2_ERROR_REQUEST_DENIED			-32
+#define LIBSSH2_ERROR_METHOD_NOT_SUPPORTED		-33
+#define LIBSSH2_ERROR_INVAL						-34
 
 /* Session API */
 LIBSSH2_API LIBSSH2_SESSION *libssh2_session_init_ex(LIBSSH2_ALLOC_FUNC((*my_alloc)), LIBSSH2_FREE_FUNC((*my_free)), LIBSSH2_REALLOC_FUNC((*my_realloc)), void *abstract);
diff --git a/src/kex.c b/src/kex.c
index c49e05b1..af68d3a5 100644
--- a/src/kex.c
+++ b/src/kex.c
@@ -1251,6 +1251,7 @@ LIBSSH2_API int libssh2_session_method_pref(LIBSSH2_SESSION *session, int method
 			mlist = NULL;
 			break;
 		default:
+			libssh2_error(session, LIBSSH2_ERROR_INVAL, "Invalid parameter specified for method_type", 0);
 			return -1;
 	}
 
@@ -1282,6 +1283,7 @@ LIBSSH2_API int libssh2_session_method_pref(LIBSSH2_SESSION *session, int method
 	}
 
 	if (strlen(newprefs) == 0) {
+		libssh2_error(session, LIBSSH2_ERROR_METHOD_NOT_SUPPORTED, "The requested method(s) are not currently supported", 0);
 		LIBSSH2_FREE(session, newprefs);
 		return -1;
 	}