diff --git a/include/proto/sample.h b/include/proto/sample.h
index 02ccc5206..6a01ed330 100644
--- a/include/proto/sample.h
+++ b/include/proto/sample.h
@@ -33,9 +33,9 @@ struct sample_conv *find_sample_conv(const char *kw, int len);
 struct sample *sample_process(struct proxy *px, struct session *sess,
                               struct stream *strm, unsigned int opt,
                               struct sample_expr *expr, struct sample *p);
-struct sample *sample_fetch_string(struct proxy *px, struct session *sess,
+struct sample *sample_fetch_as_type(struct proxy *px, struct session *sess,
                                    struct stream *strm, unsigned int opt,
-                                   struct sample_expr *expr);
+                                   struct sample_expr *expr, int smp_type);
 void sample_register_fetches(struct sample_fetch_kw_list *psl);
 void sample_register_convs(struct sample_conv_kw_list *psl);
 const char *sample_src_names(unsigned int use);
diff --git a/src/log.c b/src/log.c
index f0db0a829..577618cff 100644
--- a/src/log.c
+++ b/src/log.c
@@ -980,9 +980,9 @@ int build_logline(struct stream *s, char *dst, size_t maxsize, struct list *list
 			case LOG_FMT_EXPR: // sample expression, may be request or response
 				key = NULL;
 				if (tmp->options & LOG_OPT_REQ_CAP)
-					key = sample_fetch_string(be, sess, s, SMP_OPT_DIR_REQ|SMP_OPT_FINAL, tmp->expr);
+					key = sample_fetch_as_type(be, sess, s, SMP_OPT_DIR_REQ|SMP_OPT_FINAL, tmp->expr, SMP_T_STR);
 				if (!key && (tmp->options & LOG_OPT_RES_CAP))
-					key = sample_fetch_string(be, sess, s, SMP_OPT_DIR_RES|SMP_OPT_FINAL, tmp->expr);
+					key = sample_fetch_as_type(be, sess, s, SMP_OPT_DIR_RES|SMP_OPT_FINAL, tmp->expr, SMP_T_STR);
 				if (tmp->options & LOG_OPT_HTTP)
 					ret = encode_chunk(tmplog, dst + maxsize,
 					                   '%', http_encode_map, key ? &key->data.str : &empty);
diff --git a/src/proto_http.c b/src/proto_http.c
index 1c30b3bf4..c24479240 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -12498,7 +12498,7 @@ int http_action_req_capture(struct http_req_rule *rule, struct proxy *px, struct
 	char **cap = s->req_cap;
 	int len;
 
-	key = sample_fetch_string(s->be, sess, s, SMP_OPT_DIR_REQ|SMP_OPT_FINAL, expr);
+	key = sample_fetch_as_type(s->be, sess, s, SMP_OPT_DIR_REQ|SMP_OPT_FINAL, expr, SMP_T_STR);
 	if (!key)
 		return 1;
 
@@ -12541,7 +12541,7 @@ int http_action_req_capture_by_id(struct http_req_rule *rule, struct proxy *px,
 	if (!h)
 		return 1;
 
-	key = sample_fetch_string(s->be, sess, s, SMP_OPT_DIR_REQ|SMP_OPT_FINAL, expr);
+	key = sample_fetch_as_type(s->be, sess, s, SMP_OPT_DIR_REQ|SMP_OPT_FINAL, expr, SMP_T_STR);
 	if (!key)
 		return 1;
 
@@ -12710,7 +12710,7 @@ int http_action_res_capture_by_id(struct http_res_rule *rule, struct proxy *px,
 	if (!h)
 		return 1;
 
-	key = sample_fetch_string(s->be, sess, s, SMP_OPT_DIR_RES|SMP_OPT_FINAL, expr);
+	key = sample_fetch_as_type(s->be, sess, s, SMP_OPT_DIR_RES|SMP_OPT_FINAL, expr, SMP_T_STR);
 	if (!key)
 		return 1;
 
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 6d1ec03a9..9f9de9bae 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -1206,7 +1206,7 @@ int tcp_inspect_request(struct stream *s, struct channel *req, int an_bit)
 				char **cap = s->req_cap;
 				int len;
 
-				key = sample_fetch_string(s->be, sess, s, SMP_OPT_DIR_REQ | partial, rule->act_prm.cap.expr);
+				key = sample_fetch_as_type(s->be, sess, s, SMP_OPT_DIR_REQ | partial, rule->act_prm.cap.expr, SMP_T_STR);
 				if (!key)
 					continue;
 
diff --git a/src/sample.c b/src/sample.c
index 309ea11a2..330f08a53 100644
--- a/src/sample.c
+++ b/src/sample.c
@@ -1338,8 +1338,9 @@ int smp_resolve_args(struct proxy *p)
 /*
  * Process a fetch + format conversion as defined by the sample expression
  * <expr> on request or response considering the <opt> parameter. The output is
- * always of type string. If a stable sample can be fetched, or an unstable one
- * when <opt> contains SMP_OPT_FINAL, the sample is converted to a string and
+ * not explicitly set to <smp_type>, but shall be compatible with it as
+ * specified by 'sample_casts' table. If a stable sample can be fetched, or an
+ * unstable one when <opt> contains SMP_OPT_FINAL, the sample is converted and
  * returned without the SMP_F_MAY_CHANGE flag. If an unstable sample is found
  * and <opt> does not contain SMP_OPT_FINAL, then the sample is returned as-is
  * with its SMP_F_MAY_CHANGE flag so that the caller can check it and decide to
@@ -1355,9 +1356,9 @@ int smp_resolve_args(struct proxy *p)
  *   smp      1        0     Not present yet, may appear later (eg: header)
  *   smp      1        1     never happens (either flag is cleared on output)
  */
-struct sample *sample_fetch_string(struct proxy *px, struct session *sess,
+struct sample *sample_fetch_as_type(struct proxy *px, struct session *sess,
                                    struct stream *strm, unsigned int opt,
-                                   struct sample_expr *expr)
+                                   struct sample_expr *expr, int smp_type)
 {
 	struct sample *smp = &temp_smp;
 
@@ -1369,13 +1370,12 @@ struct sample *sample_fetch_string(struct proxy *px, struct session *sess,
 		return NULL;
 	}
 
-	if (!sample_casts[smp->type][SMP_T_STR])
+	if (!sample_casts[smp->type][smp_type])
 		return NULL;
 
-	if (!sample_casts[smp->type][SMP_T_STR](smp))
+	if (!sample_casts[smp->type][smp_type](smp))
 		return NULL;
 
-	smp->type = SMP_T_STR;
 	smp->flags &= ~SMP_F_MAY_CHANGE;
 	return smp;
 }