diff --git a/src/conf.c b/src/conf.c
index 25d80a6d..0ed3eb6f 100644
--- a/src/conf.c
+++ b/src/conf.c
@@ -1382,17 +1382,17 @@ int _config_read_file_core(struct mqtt3_config *config, bool reload, const char
 						_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error: Empty max_queued_messages value in configuration.");
 					}
 				}else if(!strcmp(token, "memory_limit")){
-					size_t lim;
+					ssize_t lim;
 					if(_conf_parse_int(&token, "memory_limit", (int *)&lim, saveptr)) return MOSQ_ERR_INVAL;
 					if(lim < 0){
-						_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error: Invalid memory_limit value (%lu).", lim);
+						_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error: Invalid memory_limit value (%ld).", lim);
 						return MOSQ_ERR_INVAL;
 					}
 					memory__set_limit(lim);
 				}else if(!strcmp(token, "message_size_limit")){
 					if(_conf_parse_int(&token, "message_size_limit", (int *)&config->message_size_limit, saveptr)) return MOSQ_ERR_INVAL;
 					if(config->message_size_limit > MQTT_MAX_PAYLOAD){
-						_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error: Invalid message_size_limit value (%d).", config->message_size_limit);
+						_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error: Invalid message_size_limit value (%u).", config->message_size_limit);
 						return MOSQ_ERR_INVAL;
 					}
 				}else if(!strcmp(token, "mount_point")){