diff --git a/include/haproxy/proxy-t.h b/include/haproxy/proxy-t.h
index 2f7bf7bbe..67a45bf94 100644
--- a/include/haproxy/proxy-t.h
+++ b/include/haproxy/proxy-t.h
@@ -92,7 +92,7 @@ enum PR_SRV_STATE_FILE {
 #define PR_O_IGNORE_PRB 0x00000200      /* ignore empty requests (aborts and timeouts) */
 #define PR_O_NULLNOLOG  0x00000400      /* a connect without request will not be logged */
 #define PR_O_WREQ_BODY  0x00000800      /* always wait for the HTTP request body */
-#define PR_O_HTTP_UPG   0x00001000      /* Contain a "switch-mode http" tcp-request rule */
+#define PR_O_HTTP_UPG   0x00001000      /* implicit (default/use backend) or explicit (switch-mode) http upgrade */
 /* unused: 0x00002000 */
 #define PR_O_PERSIST    0x00004000      /* server persistence stays effective even when server is down */
 #define PR_O_LOGASAP    0x00008000      /* log as soon as possible, without waiting for the stream to complete */
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 2744f97b7..f2fb4676b 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -3120,6 +3120,12 @@ init_proxies_list_stage1:
 						   curproxy->id);
 					err_code |= ERR_WARN;
 				}
+				if (target->mode == PR_MODE_HTTP) {
+					/* at least one of the used backends will provoke an
+					 * HTTP upgrade
+					 */
+					curproxy->options |= PR_O_HTTP_UPG;
+				}
 			}
 		}
 
@@ -3153,6 +3159,11 @@ init_proxies_list_stage1:
 				if (node->type != LOG_FMT_TEXT || node->list.n != &rule->be.expr) {
 					rule->dynamic = 1;
 					free(pxname);
+					/* backend is not yet known so we cannot assume its type,
+					 * thus we should consider that at least one of the used
+					 * backends may provoke HTTP upgrade
+					 */
+					curproxy->options |= PR_O_HTTP_UPG;
 					continue;
 				}
 				/* Only one element in the list, a simple string: free the expression and
@@ -3187,6 +3198,12 @@ init_proxies_list_stage1:
 			} else {
 				ha_free(&rule->be.name);
 				rule->be.backend = target;
+				if (target->mode == PR_MODE_HTTP) {
+					/* at least one of the used backends will provoke an
+					 * HTTP upgrade
+					 */
+					curproxy->options |= PR_O_HTTP_UPG;
+				}
 			}
 			err_code |= warnif_tcp_http_cond(curproxy, rule->cond);
 		}