diff --git a/common/Makefile b/common/Makefile
index 51f96ee6cfcb..b5a1591e9afc 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -56,6 +56,7 @@ COMMON_SRC_NOGEN :=				\
 	common/iso4217.c			\
 	common/json_blinded_path.c		\
 	common/json_channel_type.c		\
+	common/json_command.c			\
 	common/json_filter.c			\
 	common/json_param.c			\
 	common/json_parse.c			\
@@ -115,7 +116,6 @@ COMMON_HEADERS_NOGEN := $(COMMON_SRC_NOGEN:.c=.h)	\
 	common/gossip_constants.h			\
 	common/hsm_version.h				\
 	common/htlc.h					\
-	common/json_command.h				\
 	common/jsonrpc_errors.h				\
 	common/overflows.h
 
diff --git a/common/json_command.c b/common/json_command.c
new file mode 100644
index 000000000000..613b02e1d646
--- /dev/null
+++ b/common/json_command.c
@@ -0,0 +1,33 @@
+#include "config.h"
+#include <common/json_command.h>
+
+struct command_result *
+command_fail_badparam(struct command *cmd,
+		      const char *paramname,
+		      const char *buffer,
+		      const jsmntok_t *tok,
+		      const char *msg)
+{
+	if (command_dev_apis(cmd)) {
+		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+				    "%s: %s: invalid token '%.*s'",
+				    paramname, msg,
+				    json_tok_full_len(tok),
+				    json_tok_full(buffer, tok));
+	}
+
+	/* Someone misconfigured LNBITS with "" around the rune, and so the
+	 * user got a message about a bad rune parameter which *contained the
+	 * rune itself*!.  LNBITS should probably swallow any JSONRPC2_* error
+	 * itself, but it is quite possibly not the only case where this case
+	 * where this can happen.  So we are a little circumspect in this
+	 * case. */
+	command_log(cmd, LOG_INFORM,
+		    "Invalid parameter %s (%s): token '%.*s'",
+		    paramname, msg,
+		    json_tok_full_len(tok),
+		    json_tok_full(buffer, tok));
+	return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+			    "%s: %s: invalid token (see logs for details)",
+			    paramname, msg);
+}
diff --git a/common/json_command.h b/common/json_command.h
index 4e9112c85b1b..d0c0667f4281 100644
--- a/common/json_command.h
+++ b/common/json_command.h
@@ -54,35 +54,10 @@ struct command_result *command_check_done(struct command *cmd)
 	 WARN_UNUSED_RESULT;
 
 /* Convenient wrapper for "paramname: msg: invalid token '.*%s'" */
-static inline struct command_result *
-command_fail_badparam(struct command *cmd,
-		      const char *paramname,
-		      const char *buffer,
-		      const jsmntok_t *tok,
-		      const char *msg)
-{
-	if (command_dev_apis(cmd)) {
-		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
-				    "%s: %s: invalid token '%.*s'",
-				    paramname, msg,
-				    json_tok_full_len(tok),
-				    json_tok_full(buffer, tok));
-	}
-
-	/* Someone misconfigured LNBITS with "" around the rune, and so the
-	 * user got a message about a bad rune parameter which *contained the
-	 * rune itself*!.  LNBITS should probably swallow any JSONRPC2_* error
-	 * itself, but it is quite possibly not the only case where this case
-	 * where this can happen.  So we are a little circumspect in this
-	 * case. */
-	command_log(cmd, LOG_INFORM,
-		    "Invalid parameter %s (%s): token '%.*s'",
-		    paramname, msg,
-		    json_tok_full_len(tok),
-		    json_tok_full(buffer, tok));
-	return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
-			    "%s: %s: invalid token (see logs for details)",
-			    paramname, msg);
-}
+struct command_result *command_fail_badparam(struct command *cmd,
+					     const char *paramname,
+					     const char *buffer,
+					     const jsmntok_t *tok,
+					     const char *msg);
 
 #endif /* LIGHTNING_COMMON_JSON_COMMAND_H */
diff --git a/common/test/run-json_filter.c b/common/test/run-json_filter.c
index 233f7e54078f..d4e68801a637 100644
--- a/common/test/run-json_filter.c
+++ b/common/test/run-json_filter.c
@@ -33,11 +33,13 @@ struct command_result *command_fail(struct command *cmd UNNEEDED, enum jsonrpc_e
 				    const char *fmt UNNEEDED, ...)
 
 { fprintf(stderr, "command_fail called!\n"); abort(); }
-/* Generated stub for command_log */
-void command_log(struct command *cmd UNNEEDED, enum log_level level UNNEEDED,
-		 const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_log called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for command_set_usage */
 void command_set_usage(struct command *cmd UNNEEDED, const char *usage UNNEEDED)
 { fprintf(stderr, "command_set_usage called!\n"); abort(); }
diff --git a/common/test/run-json_remove.c b/common/test/run-json_remove.c
index 422c580cb16f..93c844143415 100644
--- a/common/test/run-json_remove.c
+++ b/common/test/run-json_remove.c
@@ -62,11 +62,13 @@ struct command_result *command_fail(struct command *cmd UNNEEDED, enum jsonrpc_e
 				    const char *fmt UNNEEDED, ...)
 
 { fprintf(stderr, "command_fail called!\n"); abort(); }
-/* Generated stub for command_log */
-void command_log(struct command *cmd UNNEEDED, enum log_level level UNNEEDED,
-		 const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_log called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for command_set_usage */
 void command_set_usage(struct command *cmd UNNEEDED, const char *usage UNNEEDED)
 { fprintf(stderr, "command_set_usage called!\n"); abort(); }
diff --git a/common/test/run-json_stream-filter.c b/common/test/run-json_stream-filter.c
index cebca0f9cf55..1e484b475868 100644
--- a/common/test/run-json_stream-filter.c
+++ b/common/test/run-json_stream-filter.c
@@ -50,22 +50,16 @@ struct amount_asset amount_sat_to_asset(struct amount_sat *sat UNNEEDED, const u
 /* Generated stub for amount_tx_fee */
 struct amount_sat amount_tx_fee(u32 fee_per_kw UNNEEDED, size_t weight UNNEEDED)
 { fprintf(stderr, "amount_tx_fee called!\n"); abort(); }
-/* Generated stub for command_dev_apis */
-bool command_dev_apis(const struct command *cmd UNNEEDED)
-{ fprintf(stderr, "command_dev_apis called!\n"); abort(); }
-/* Generated stub for command_fail */
-struct command_result *command_fail(struct command *cmd UNNEEDED, enum jsonrpc_errcode code UNNEEDED,
-				    const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_fail called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for command_filter_ptr */
 struct json_filter **command_filter_ptr(struct command *cmd UNNEEDED)
 { fprintf(stderr, "command_filter_ptr called!\n"); abort(); }
-/* Generated stub for command_log */
-void command_log(struct command *cmd UNNEEDED, enum log_level level UNNEEDED,
-		 const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_log called!\n"); abort(); }
 /* Generated stub for fmt_amount_sat */
 char *fmt_amount_sat(const tal_t *ctx UNNEEDED, struct amount_sat sat UNNEEDED)
 { fprintf(stderr, "fmt_amount_sat called!\n"); abort(); }
diff --git a/common/test/run-param.c b/common/test/run-param.c
index 38cbd8b31f37..3cb94bf854c7 100644
--- a/common/test/run-param.c
+++ b/common/test/run-param.c
@@ -1,5 +1,6 @@
 #include "config.h"
 #include "../bech32.c"
+#include "../json_command.c"
 #include "../json_filter.c"
 #include "../json_parse.c"
 #include "../json_parse_simple.c"
@@ -56,14 +57,17 @@ bool command_deprecated_in_ok(struct command *cmd,
 	return true;
 }
 
+/* Generated stub for command_dev_apis */
+bool command_dev_apis(const struct command *cmd)
+{
+	return true;
+}
+
 /* AUTOGENERATED MOCKS START */
 /* Generated stub for command_check_done */
 struct command_result *command_check_done(struct command *cmd)
 
 { fprintf(stderr, "command_check_done called!\n"); abort(); }
-/* Generated stub for command_dev_apis */
-bool command_dev_apis(const struct command *cmd UNNEEDED)
-{ fprintf(stderr, "command_dev_apis called!\n"); abort(); }
 /* Generated stub for command_filter_ptr */
 struct json_filter **command_filter_ptr(struct command *cmd UNNEEDED)
 { fprintf(stderr, "command_filter_ptr called!\n"); abort(); }
diff --git a/lightningd/Makefile b/lightningd/Makefile
index 0c8aa0ba5a68..e9766343b60b 100644
--- a/lightningd/Makefile
+++ b/lightningd/Makefile
@@ -116,6 +116,7 @@ LIGHTNINGD_COMMON_OBJS :=			\
 	common/key_derive.o			\
 	common/keyset.o				\
 	common/json_channel_type.o		\
+	common/json_command.o			\
 	common/json_filter.o			\
 	common/json_param.o			\
 	common/json_parse.o			\
diff --git a/lightningd/test/run-invoice-select-inchan.c b/lightningd/test/run-invoice-select-inchan.c
index aa48c84c368f..1b3dec608cf7 100644
--- a/lightningd/test/run-invoice-select-inchan.c
+++ b/lightningd/test/run-invoice-select-inchan.c
@@ -156,14 +156,18 @@ bool command_deprecated_out_ok(struct command *cmd UNNEEDED,
 			       const char *depr_start UNNEEDED,
 			       const char *depr_end UNNEEDED)
 { fprintf(stderr, "command_deprecated_out_ok called!\n"); abort(); }
-/* Generated stub for command_dev_apis */
-bool command_dev_apis(const struct command *cmd UNNEEDED)
-{ fprintf(stderr, "command_dev_apis called!\n"); abort(); }
 /* Generated stub for command_fail */
 struct command_result *command_fail(struct command *cmd UNNEEDED, enum jsonrpc_errcode code UNNEEDED,
 				    const char *fmt UNNEEDED, ...)
 
 { fprintf(stderr, "command_fail called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for command_failed */
 struct command_result *command_failed(struct command *cmd UNNEEDED,
 				      struct json_stream *result)
@@ -172,11 +176,6 @@ struct command_result *command_failed(struct command *cmd UNNEEDED,
 /* Generated stub for command_its_complicated */
 struct command_result *command_its_complicated(const char *why UNNEEDED)
 { fprintf(stderr, "command_its_complicated called!\n"); abort(); }
-/* Generated stub for command_log */
-void command_log(struct command *cmd UNNEEDED, enum log_level level UNNEEDED,
-		 const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_log called!\n"); abort(); }
 /* Generated stub for command_logger */
 struct logger *command_logger(struct command *cmd UNNEEDED)
 { fprintf(stderr, "command_logger called!\n"); abort(); }
diff --git a/lightningd/test/run-jsonrpc.c b/lightningd/test/run-jsonrpc.c
index 3b2772e53ec2..4975d66b326b 100644
--- a/lightningd/test/run-jsonrpc.c
+++ b/lightningd/test/run-jsonrpc.c
@@ -7,6 +7,13 @@
 #include <stdio.h>
 
 /* AUTOGENERATED MOCKS START */
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for db_begin_transaction_ */
 void db_begin_transaction_(struct db *db UNNEEDED, const char *location UNNEEDED)
 { fprintf(stderr, "db_begin_transaction_ called!\n"); abort(); }
diff --git a/lightningd/test/run-log-pruning.c b/lightningd/test/run-log-pruning.c
index 149ffa17a1ff..7e2c2756552d 100644
--- a/lightningd/test/run-log-pruning.c
+++ b/lightningd/test/run-log-pruning.c
@@ -3,19 +3,13 @@
 #include <common/setup.h>
 
 /* AUTOGENERATED MOCKS START */
-/* Generated stub for command_dev_apis */
-bool command_dev_apis(const struct command *cmd UNNEEDED)
-{ fprintf(stderr, "command_dev_apis called!\n"); abort(); }
-/* Generated stub for command_fail */
-struct command_result *command_fail(struct command *cmd UNNEEDED, enum jsonrpc_errcode code UNNEEDED,
-				    const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_fail called!\n"); abort(); }
-/* Generated stub for command_log */
-void command_log(struct command *cmd UNNEEDED, enum log_level level UNNEEDED,
-		 const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_log called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for command_param_failed */
 struct command_result *command_param_failed(void)
 
diff --git a/lightningd/test/run-log_filter.c b/lightningd/test/run-log_filter.c
index 81f7c37af01d..1d373cbd227e 100644
--- a/lightningd/test/run-log_filter.c
+++ b/lightningd/test/run-log_filter.c
@@ -14,19 +14,13 @@ void notify_log(struct lightningd *ld UNNEEDED, const struct log_entry *l UNNEED
 {  }
 
 /* AUTOGENERATED MOCKS START */
-/* Generated stub for command_dev_apis */
-bool command_dev_apis(const struct command *cmd UNNEEDED)
-{ fprintf(stderr, "command_dev_apis called!\n"); abort(); }
-/* Generated stub for command_fail */
-struct command_result *command_fail(struct command *cmd UNNEEDED, enum jsonrpc_errcode code UNNEEDED,
-				    const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_fail called!\n"); abort(); }
-/* Generated stub for command_log */
-void command_log(struct command *cmd UNNEEDED, enum log_level level UNNEEDED,
-		 const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_log called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for command_param_failed */
 struct command_result *command_param_failed(void)
 
diff --git a/plugins/Makefile b/plugins/Makefile
index 3c34f72481e0..e7530431e4a4 100644
--- a/plugins/Makefile
+++ b/plugins/Makefile
@@ -159,6 +159,7 @@ PLUGIN_COMMON_OBJS :=				\
 	common/deprecation.o			\
 	common/features.o			\
 	common/hash_u5.o			\
+	common/json_command.o			\
 	common/json_param.o			\
 	common/json_parse.o			\
 	common/json_parse_simple.o		\
diff --git a/plugins/bkpr/test/run-bkpr_db.c b/plugins/bkpr/test/run-bkpr_db.c
index bd9104d80ff4..308110548ec1 100644
--- a/plugins/bkpr/test/run-bkpr_db.c
+++ b/plugins/bkpr/test/run-bkpr_db.c
@@ -24,6 +24,13 @@
 /* Generated stub for account_entry_tag_str */
 const char *account_entry_tag_str(enum account_entry_tag tag UNNEEDED)
 { fprintf(stderr, "account_entry_tag_str called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for daemon_developer_mode */
 bool daemon_developer_mode(char *argv[])
 { fprintf(stderr, "daemon_developer_mode called!\n"); abort(); }
diff --git a/plugins/bkpr/test/run-recorder.c b/plugins/bkpr/test/run-recorder.c
index 62c317746102..5ebac38ab05e 100644
--- a/plugins/bkpr/test/run-recorder.c
+++ b/plugins/bkpr/test/run-recorder.c
@@ -30,6 +30,13 @@
 /* Generated stub for account_entry_tag_str */
 const char *account_entry_tag_str(enum account_entry_tag tag UNNEEDED)
 { fprintf(stderr, "account_entry_tag_str called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for daemon_developer_mode */
 bool daemon_developer_mode(char *argv[])
 { fprintf(stderr, "daemon_developer_mode called!\n"); abort(); }
diff --git a/wallet/test/run-wallet.c b/wallet/test/run-wallet.c
index 915b4100b1ce..87633de95b2f 100644
--- a/wallet/test/run-wallet.c
+++ b/wallet/test/run-wallet.c
@@ -135,24 +135,23 @@ bool command_deprecated_out_ok(struct command *cmd UNNEEDED,
 			       const char *depr_start UNNEEDED,
 			       const char *depr_end UNNEEDED)
 { fprintf(stderr, "command_deprecated_out_ok called!\n"); abort(); }
-/* Generated stub for command_dev_apis */
-bool command_dev_apis(const struct command *cmd UNNEEDED)
-{ fprintf(stderr, "command_dev_apis called!\n"); abort(); }
 /* Generated stub for command_fail */
 struct command_result *command_fail(struct command *cmd UNNEEDED, enum jsonrpc_errcode code UNNEEDED,
 				    const char *fmt UNNEEDED, ...)
 
 { fprintf(stderr, "command_fail called!\n"); abort(); }
+/* Generated stub for command_fail_badparam */
+struct command_result *command_fail_badparam(struct command *cmd UNNEEDED,
+					     const char *paramname UNNEEDED,
+					     const char *buffer UNNEEDED,
+					     const jsmntok_t *tok UNNEEDED,
+					     const char *msg UNNEEDED)
+{ fprintf(stderr, "command_fail_badparam called!\n"); abort(); }
 /* Generated stub for command_failed */
 struct command_result *command_failed(struct command *cmd UNNEEDED,
 				      struct json_stream *result)
 
 { fprintf(stderr, "command_failed called!\n"); abort(); }
-/* Generated stub for command_log */
-void command_log(struct command *cmd UNNEEDED, enum log_level level UNNEEDED,
-		 const char *fmt UNNEEDED, ...)
-
-{ fprintf(stderr, "command_log called!\n"); abort(); }
 /* Generated stub for command_param_failed */
 struct command_result *command_param_failed(void)
 
@@ -599,9 +598,6 @@ bool json_tok_channel_id(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEE
 /* Generated stub for json_tok_full */
 const char *json_tok_full(const char *buffer UNNEEDED, const jsmntok_t *t UNNEEDED)
 { fprintf(stderr, "json_tok_full called!\n"); abort(); }
-/* Generated stub for json_tok_full_len */
-int json_tok_full_len(const jsmntok_t *t UNNEEDED)
-{ fprintf(stderr, "json_tok_full_len called!\n"); abort(); }
 /* Generated stub for json_tok_streq */
 bool json_tok_streq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED, const char *str UNNEEDED)
 { fprintf(stderr, "json_tok_streq called!\n"); abort(); }