diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index 736f666..172dfbd 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -494,6 +494,7 @@
 		enum object_type type;
 		unsigned long size, len;
 		char *buf = read_object_file(oid, &type, &size);
+		struct signature_check sigc = { 0 };
 		struct strbuf sig = STRBUF_INIT;
 
 		if (!buf || type != OBJ_TAG)
@@ -502,10 +503,12 @@
 
 		if (size == len)
 			; /* merely annotated */
-		else if (verify_signed_buffer(buf, len, buf + len, size - len, &sig, NULL)) {
-			if (!sig.len)
-				strbuf_addstr(&sig, "gpg verification failed.\n");
-		}
+		else if (check_signature(buf, len, buf + len, size - len, &sigc) &&
+			!sigc.gpg_output)
+			strbuf_addstr(&sig, "gpg verification failed.\n");
+		else
+			strbuf_addstr(&sig, sigc.gpg_output);
+		signature_check_clear(&sigc);
 
 		if (!tag_number++) {
 			fmt_tag_signature(&tagbuf, &sig, buf, len);
diff --git a/gpg-interface.c b/gpg-interface.c
index 165274d..2d538bc 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -256,6 +256,55 @@
 	FREE_AND_NULL(sigc->key);
 }
 
+static int verify_signed_buffer(const char *payload, size_t payload_size,
+				const char *signature, size_t signature_size,
+				struct strbuf *gpg_output,
+				struct strbuf *gpg_status)
+{
+	struct child_process gpg = CHILD_PROCESS_INIT;
+	struct gpg_format *fmt;
+	struct tempfile *temp;
+	int ret;
+	struct strbuf buf = STRBUF_INIT;
+
+	temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
+	if (!temp)
+		return error_errno(_("could not create temporary file"));
+	if (write_in_full(temp->fd, signature, signature_size) < 0 ||
+	    close_tempfile_gently(temp) < 0) {
+		error_errno(_("failed writing detached signature to '%s'"),
+			    temp->filename.buf);
+		delete_tempfile(&temp);
+		return -1;
+	}
+
+	fmt = get_format_by_sig(signature);
+	if (!fmt)
+		BUG("bad signature '%s'", signature);
+
+	argv_array_push(&gpg.args, fmt->program);
+	argv_array_pushv(&gpg.args, fmt->verify_args);
+	argv_array_pushl(&gpg.args,
+			 "--status-fd=1",
+			 "--verify", temp->filename.buf, "-",
+			 NULL);
+
+	if (!gpg_status)
+		gpg_status = &buf;
+
+	sigchain_push(SIGPIPE, SIG_IGN);
+	ret = pipe_command(&gpg, payload, payload_size,
+			   gpg_status, 0, gpg_output, 0);
+	sigchain_pop(SIGPIPE);
+
+	delete_tempfile(&temp);
+
+	ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
+	strbuf_release(&buf); /* no matter it was used or not */
+
+	return ret;
+}
+
 int check_signature(const char *payload, size_t plen, const char *signature,
 	size_t slen, struct signature_check *sigc)
 {
@@ -418,51 +467,3 @@
 
 	return 0;
 }
-
-int verify_signed_buffer(const char *payload, size_t payload_size,
-			 const char *signature, size_t signature_size,
-			 struct strbuf *gpg_output, struct strbuf *gpg_status)
-{
-	struct child_process gpg = CHILD_PROCESS_INIT;
-	struct gpg_format *fmt;
-	struct tempfile *temp;
-	int ret;
-	struct strbuf buf = STRBUF_INIT;
-
-	temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
-	if (!temp)
-		return error_errno(_("could not create temporary file"));
-	if (write_in_full(temp->fd, signature, signature_size) < 0 ||
-	    close_tempfile_gently(temp) < 0) {
-		error_errno(_("failed writing detached signature to '%s'"),
-			    temp->filename.buf);
-		delete_tempfile(&temp);
-		return -1;
-	}
-
-	fmt = get_format_by_sig(signature);
-	if (!fmt)
-		BUG("bad signature '%s'", signature);
-
-	argv_array_push(&gpg.args, fmt->program);
-	argv_array_pushv(&gpg.args, fmt->verify_args);
-	argv_array_pushl(&gpg.args,
-			 "--status-fd=1",
-			 "--verify", temp->filename.buf, "-",
-			 NULL);
-
-	if (!gpg_status)
-		gpg_status = &buf;
-
-	sigchain_push(SIGPIPE, SIG_IGN);
-	ret = pipe_command(&gpg, payload, payload_size,
-			   gpg_status, 0, gpg_output, 0);
-	sigchain_pop(SIGPIPE);
-
-	delete_tempfile(&temp);
-
-	ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
-	strbuf_release(&buf); /* no matter it was used or not */
-
-	return ret;
-}
diff --git a/gpg-interface.h b/gpg-interface.h
index 796571e..f4e9b4f 100644
--- a/gpg-interface.h
+++ b/gpg-interface.h
@@ -54,15 +54,6 @@
 int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
 		const char *signing_key);
 
-/*
- * Run "gpg" to see if the payload matches the detached signature.
- * gpg_output, when set, receives the diagnostic output from GPG.
- * gpg_status, when set, receives the status output from GPG.
- */
-int verify_signed_buffer(const char *payload, size_t payload_size,
-			 const char *signature, size_t signature_size,
-			 struct strbuf *gpg_output, struct strbuf *gpg_status);
-
 int git_gpg_config(const char *, const char *, void *);
 void set_signing_key(const char *);
 const char *get_signing_key(void);
diff --git a/log-tree.c b/log-tree.c
index 5425ae9..f1ac5a6 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -449,22 +449,21 @@
 {
 	struct strbuf payload = STRBUF_INIT;
 	struct strbuf signature = STRBUF_INIT;
-	struct strbuf gpg_output = STRBUF_INIT;
+	struct signature_check sigc = { 0 };
 	int status;
 
 	if (parse_signed_commit(commit, &payload, &signature) <= 0)
 		goto out;
 
-	status = verify_signed_buffer(payload.buf, payload.len,
-				      signature.buf, signature.len,
-				      &gpg_output, NULL);
-	if (status && !gpg_output.len)
-		strbuf_addstr(&gpg_output, "No signature\n");
-
-	show_sig_lines(opt, status, gpg_output.buf);
+	status = check_signature(payload.buf, payload.len, signature.buf,
+				 signature.len, &sigc);
+	if (status && !sigc.gpg_output)
+		show_sig_lines(opt, status, "No signature\n");
+	else
+		show_sig_lines(opt, status, sigc.gpg_output);
+	signature_check_clear(&sigc);
 
  out:
-	strbuf_release(&gpg_output);
 	strbuf_release(&payload);
 	strbuf_release(&signature);
 }
@@ -497,8 +496,9 @@
 	struct object_id oid;
 	struct tag *tag;
 	struct strbuf verify_message;
+	struct signature_check sigc = { 0 };
 	int status, nth;
-	size_t payload_size, gpg_message_offset;
+	size_t payload_size;
 
 	hash_object_file(the_hash_algo, extra->value, extra->len,
 			 type_name(OBJ_TAG), &oid);
@@ -520,19 +520,19 @@
 	else
 		strbuf_addf(&verify_message,
 			    "parent #%d, tagged '%s'\n", nth + 1, tag->tag);
-	gpg_message_offset = verify_message.len;
 
 	payload_size = parse_signature(extra->value, extra->len);
 	status = -1;
 	if (extra->len > payload_size) {
 		/* could have a good signature */
-		if (!verify_signed_buffer(extra->value, payload_size,
-					  extra->value + payload_size,
-					  extra->len - payload_size,
-					  &verify_message, NULL))
-			status = 0; /* good */
-		else if (verify_message.len <= gpg_message_offset)
+		status = check_signature(extra->value, payload_size,
+					 extra->value + payload_size,
+					 extra->len - payload_size, &sigc);
+		if (sigc.gpg_output)
+			strbuf_addstr(&verify_message, sigc.gpg_output);
+		else
 			strbuf_addstr(&verify_message, "No signature\n");
+		signature_check_clear(&sigc);
 		/* otherwise we couldn't verify, which is shown as bad */
 	}