diff --git a/include/proto/pattern.h b/include/proto/pattern.h
index 450a8dbac..e9269e4eb 100644
--- a/include/proto/pattern.h
+++ b/include/proto/pattern.h
@@ -174,8 +174,8 @@ struct pat_ref *pat_ref_new(const char *reference, const char *display, unsigned
 struct pat_ref *pat_ref_newid(int unique_id, const char *display, unsigned int flags);
 int pat_ref_append(struct pat_ref *ref, char *pattern, char *sample, int line);
 int pat_ref_add(struct pat_ref *ref, const char *pattern, const char *sample, char **err);
-int pat_ref_set(struct pat_ref *ref, const char *pattern, const char *sample);
-int pat_ref_set_by_id(struct pat_ref *ref, struct pat_ref_elt *refelt, const char *value);
+int pat_ref_set(struct pat_ref *ref, const char *pattern, const char *sample, char **err);
+int pat_ref_set_by_id(struct pat_ref *ref, struct pat_ref_elt *refelt, const char *value, char **err);
 int pat_ref_delete(struct pat_ref *ref, const char *key);
 int pat_ref_delete_by_id(struct pat_ref *ref, struct pat_ref_elt *refelt);
 void pat_ref_prune(struct pat_ref *ref);
diff --git a/include/types/stream_interface.h b/include/types/stream_interface.h
index 8049fcc70..e06063410 100644
--- a/include/types/stream_interface.h
+++ b/include/types/stream_interface.h
@@ -137,6 +137,7 @@ struct appctx {
 		} table;
 		struct {
 			const char *msg;	/* pointer to a persistent message to be returned in PRINT state */
+			char *err;        /* pointer to a 'must free' message to be returned in PRINT_FREE state */
 		} cli;
 		struct {
 			void *ptr;              /* multi-purpose pointer for peers */
diff --git a/src/dumpstats.c b/src/dumpstats.c
index d9632b769..a796cd70b 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -72,6 +72,7 @@ enum {
 	STAT_CLI_OUTPUT,     /* all states after this one are responses */
 	STAT_CLI_PROMPT,     /* display the prompt (first output, same code) */
 	STAT_CLI_PRINT,      /* display message in cli->msg */
+	STAT_CLI_PRINT_FREE, /* display message in cli->msg. After the display, free the pointer */
 	STAT_CLI_O_INFO,     /* dump info */
 	STAT_CLI_O_SESS,     /* dump sessions */
 	STAT_CLI_O_ERR,      /* dump errors */
@@ -1615,6 +1616,8 @@ static int stats_sock_parse_request(struct stream_interface *si, char *line)
 			stats_sock_table_request(si, args, STAT_CLI_O_SET);
 		}
 		else if (strcmp(args[1], "map") == 0) {
+			char *err;
+
 			/* Set flags. */
 			appctx->ctx.map.display_flags = PAT_REF_MAP;
 
@@ -1658,9 +1661,12 @@ static int stats_sock_parse_request(struct stream_interface *si, char *line)
 				}
 
 				/* Try to delete the entry. */
-				if (!pat_ref_set_by_id(appctx->ctx.map.ref, ref, args[4])) {
-					appctx->ctx.cli.msg = "Pattern not found.\n";
-					appctx->st0 = STAT_CLI_PRINT;
+				err = NULL;
+				if (!pat_ref_set_by_id(appctx->ctx.map.ref, ref, args[4], &err)) {
+					if (err)
+						memprintf(&err, "%s.\n", err);
+					appctx->ctx.cli.err = err;
+					appctx->st0 = STAT_CLI_PRINT_FREE;
 					return 1;
 				}
 			}
@@ -1668,9 +1674,12 @@ static int stats_sock_parse_request(struct stream_interface *si, char *line)
 				/* Else, use the entry identifier as pattern
 				 * string, and update the value.
 				 */
-				if (!pat_ref_set(appctx->ctx.map.ref, args[3], args[4])) {
-					appctx->ctx.cli.msg = "Pattern not found.\n";
-					appctx->st0 = STAT_CLI_PRINT;
+				err = NULL;
+				if (!pat_ref_set(appctx->ctx.map.ref, args[3], args[4], &err)) {
+					if (err)
+						memprintf(&err, "%s.\n", err);
+					appctx->ctx.cli.err = err;
+					appctx->st0 = STAT_CLI_PRINT_FREE;
 					return 1;
 				}
 			}
@@ -1995,6 +2004,7 @@ static int stats_sock_parse_request(struct stream_interface *si, char *line)
 		if (strcmp(args[1], "map") == 0 ||
 		    strcmp(args[1], "acl") == 0) {
 			int ret;
+			char *err;
 
 			/* Set flags. */
 			if (args[1][0] == 'm')
@@ -2032,13 +2042,16 @@ static int stats_sock_parse_request(struct stream_interface *si, char *line)
 			}
 
 			/* Add value. */
+			err = NULL;
 			if (appctx->ctx.map.display_flags == PAT_REF_MAP)
-				ret = pat_ref_add(appctx->ctx.map.ref, args[3], args[4], NULL);
+				ret = pat_ref_add(appctx->ctx.map.ref, args[3], args[4], &err);
 			else
-				ret = pat_ref_add(appctx->ctx.map.ref, args[3], NULL, NULL);
+				ret = pat_ref_add(appctx->ctx.map.ref, args[3], NULL, &err);
 			if (!ret) {
-				appctx->ctx.cli.msg = "Out of memory error.\n";
-				appctx->st0 = STAT_CLI_PRINT;
+				if (err)
+					memprintf(&err, "%s.\n", err);
+				appctx->ctx.cli.err = err;
+				appctx->st0 = STAT_CLI_PRINT_FREE;
 				return 1;
 			}
 
@@ -2174,6 +2187,12 @@ static void cli_io_handler(struct stream_interface *si)
 				if (bi_putstr(si->ib, appctx->ctx.cli.msg) != -1)
 					appctx->st0 = STAT_CLI_PROMPT;
 				break;
+			case STAT_CLI_PRINT_FREE:
+				if (bi_putstr(si->ib, appctx->ctx.cli.err) != -1) {
+					free(appctx->ctx.cli.err);
+					appctx->st0 = STAT_CLI_PROMPT;
+				}
+				break;
 			case STAT_CLI_O_INFO:
 				if (stats_dump_info_to_buffer(si))
 					appctx->st0 = STAT_CLI_PROMPT;
@@ -5295,6 +5314,9 @@ static void cli_release_handler(struct stream_interface *si)
 		if (!LIST_ISEMPTY(&appctx->ctx.sess.bref.users))
 			LIST_DEL(&appctx->ctx.sess.bref.users);
 	}
+	else if (appctx->st0 == STAT_CLI_PRINT_FREE) {
+		free(appctx->ctx.cli.err);
+	}
 	else if (appctx->st0 == STAT_CLI_O_MLOOK) {
 		free(appctx->ctx.map.chunk.str);
 	}
diff --git a/src/pattern.c b/src/pattern.c
index 4a3b05ad4..306193e0c 100644
--- a/src/pattern.c
+++ b/src/pattern.c
@@ -1397,7 +1397,7 @@ int pat_ref_delete(struct pat_ref *ref, const char *key)
 
   /* This function modify the sample of the first pattern that match the <key>. */
 static inline int pat_ref_set_elt(struct pat_ref *ref, struct pat_ref_elt *elt,
-                                  const char *value)
+                                  const char *value, char **err)
 {
 	struct pattern_expr *expr;
 	struct sample_storage **smp;
@@ -1406,8 +1406,10 @@ static inline int pat_ref_set_elt(struct pat_ref *ref, struct pat_ref_elt *elt,
 
 	/* Modify pattern from reference. */
 	sample = strdup(value);
-	if (!sample)
+	if (!sample) {
+		memprintf(err, "out of memory error");
 		return 0;
+	}
 	free(elt->sample);
 	elt->sample = sample;
 
@@ -1419,6 +1421,7 @@ static inline int pat_ref_set_elt(struct pat_ref *ref, struct pat_ref_elt *elt,
 		smp = pattern_find_smp(expr, elt);
 		if (smp && *smp) {
 			if (!expr->pat_head->parse_smp(sample, *smp)) {
+				memprintf(err, "failed to parse sample");
 				*smp = NULL;
 				ret = 0;
 			}
@@ -1429,34 +1432,59 @@ static inline int pat_ref_set_elt(struct pat_ref *ref, struct pat_ref_elt *elt,
 }
 
 /* This function modify the sample of the first pattern that match the <key>. */
-int pat_ref_set_by_id(struct pat_ref *ref, struct pat_ref_elt *refelt, const char *value)
+int pat_ref_set_by_id(struct pat_ref *ref, struct pat_ref_elt *refelt, const char *value, char **err)
 {
 	struct pat_ref_elt *elt;
 
 	/* Look for pattern in the reference. */
 	list_for_each_entry(elt, &ref->head, list) {
 		if (elt == refelt) {
-			pat_ref_set_elt(ref, elt, value);
+			if (!pat_ref_set_elt(ref, elt, value, err))
+				return 0;
 			return 1;
 		}
 	}
+
+	memprintf(err, "key or pattern not found");
 	return 0;
 }
 
 /* This function modify the sample of the first pattern that match the <key>. */
-int pat_ref_set(struct pat_ref *ref, const char *key, const char *value)
+int pat_ref_set(struct pat_ref *ref, const char *key, const char *value, char **err)
 {
 	struct pat_ref_elt *elt;
-	int ret = 0;
+	int found = 0;
+	char *_merr;
+	char **merr;
+
+	if (err) {
+		merr = &_merr;
+		*merr = NULL;
+	}
+	else
+		merr = NULL;
 
 	/* Look for pattern in the reference. */
 	list_for_each_entry(elt, &ref->head, list) {
 		if (strcmp(key, elt->pattern) == 0) {
-			pat_ref_set_elt(ref, elt, value);
-			ret = 1;
+			if (!pat_ref_set_elt(ref, elt, value, merr)) {
+				if (!found)
+					*err = *merr;
+				else {
+					memprintf(err, "%s, %s", *err, *merr);
+					free(*merr);
+					*merr = NULL;
+				}
+			}
+			found = 1;
 		}
 	}
-	return ret;
+
+	if (!found) {
+		memprintf(err, "entry not found");
+		return 0;
+	}
+	return 1;
 }
 
 /* This function create new reference. <ref> is the reference name.