diff --git a/plugins/autoclean.c b/plugins/autoclean.c
index b076a8b38..1f4b870f0 100644
--- a/plugins/autoclean.c
+++ b/plugins/autoclean.c
@@ -46,7 +46,7 @@ static struct command_result *json_autocleaninvoice(struct command *cmd,
 		   p_opt_def("cycle_seconds", param_u64, &cycle, 3600),
 		   p_opt_def("expired_by", param_u64, &exby, 86400),
 		   NULL))
-		return NULL;
+		return command_param_failed();
 
 	cycle_seconds = *cycle;
 	expired_by = *exby;
diff --git a/plugins/fundchannel.c b/plugins/fundchannel.c
index 60459edd2..a213138c0 100644
--- a/plugins/fundchannel.c
+++ b/plugins/fundchannel.c
@@ -385,7 +385,7 @@ static struct command_result *json_fundchannel(struct command *cmd,
 		   p_opt_def("minconf", param_number, &fr->minconf, 1),
 		   p_opt("utxos", param_string, &fr->utxo_str),
 		   NULL))
-		return NULL;
+		return command_param_failed();
 
 	fr->funding_all = streq(fr->funding_str, "all");
 
diff --git a/plugins/libplugin.c b/plugins/libplugin.c
index d026c22fd..02094939d 100644
--- a/plugins/libplugin.c
+++ b/plugins/libplugin.c
@@ -636,7 +636,7 @@ static void setup_command_usage(const struct plugin_command *commands,
 
 		usage_cmd->methodname = commands[i].name;
 		res = commands[i].handle(usage_cmd, NULL, NULL);
-		assert(res == NULL);
+		assert(res == &complete);
 		assert(strmap_get(&usagemap, commands[i].name));
 	}
 }
diff --git a/plugins/pay.c b/plugins/pay.c
index eb773c2ef..8244ba82a 100644
--- a/plugins/pay.c
+++ b/plugins/pay.c
@@ -1027,7 +1027,7 @@ static struct command_result *json_pay(struct command *cmd,
 			     maxdelay_default),
 		   p_opt_def("exemptfee", param_msat, &exemptfee, AMOUNT_MSAT(5000)),
 		   NULL))
-		return NULL;
+		return command_param_failed();
 
 	b11 = bolt11_decode(cmd, b11str, NULL, &fail);
 	if (!b11) {
@@ -1158,7 +1158,7 @@ static struct command_result *json_paystatus(struct command *cmd,
 	if (!param(cmd, buf, params,
 		   p_opt("bolt11", param_string, &b11str),
 		   NULL))
-		return NULL;
+		return command_param_failed();
 
 	ret = json_out_new(NULL);
 	json_out_start(ret, NULL, '{');
@@ -1280,7 +1280,7 @@ static struct command_result *json_listpays(struct command *cmd,
 	if (!param(cmd, buf, params,
 		   p_opt("bolt11", param_string, &b11str),
 		   NULL))
-		return NULL;
+		return command_param_failed();
 
 	return send_outreq(cmd, "listsendpays",
 			   listsendpays_done, forward_error,