diff --git a/client/client_shared.c b/client/client_shared.c
index 091bd799..bca837ed 100644
--- a/client/client_shared.c
+++ b/client/client_shared.c
@@ -689,8 +689,8 @@ int client_config_line_proc(struct mosq_config *cfg, int pub_or_sub, int argc, c
 				return 1;
 			}else{
 				cfg->keepalive = atoi(argv[i+1]);
-				if(cfg->keepalive>65535){
-					fprintf(stderr, "Error: Invalid keepalive given: %d\n", cfg->keepalive);
+				if(cfg->keepalive<5 || cfg->keepalive>UINT16_MAX){
+					fprintf(stderr, "Error: Invalid keepalive given, it must be between 5 and 65535 inclusive.\n\n");
 					return 1;
 				}
 			}
diff --git a/lib/connect.c b/lib/connect.c
index efe82907..ddec8210 100644
--- a/lib/connect.c
+++ b/lib/connect.c
@@ -43,7 +43,7 @@ static int mosquitto__connect_init(struct mosquitto *mosq, const char *host, int
 
 	if(!mosq) return MOSQ_ERR_INVAL;
 	if(!host || port < 0 || port > UINT16_MAX) return MOSQ_ERR_INVAL;
-	if(keepalive < 5 || keepalive > UINT16_MAX) return MOSQ_ERR_INVAL;
+	if(keepalive != 0 && (keepalive < 5 || keepalive > UINT16_MAX)) return MOSQ_ERR_INVAL;
 
 	/* Only MQTT v3.1 requires a client id to be sent */
 	if(mosq->id == NULL && (mosq->protocol == mosq_p_mqtt31)){