diff --git a/doc/configuration.txt b/doc/configuration.txt
index 72c4680b1..e37f84cf6 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -853,8 +853,9 @@ Example:
        profiling.memory on
    .endif
 
-Three other directives are provided to report some status:
+Four other directives are provided to report some status:
 
+  - .diag "message"    : emit this message only when in diagnostic mode (-dD)
   - .notice "message"  : emit this message at level NOTICE
   - .warning "message" : emit this message at level WARNING
   - .alert "message"   : emit this message at level ALERT
@@ -880,6 +881,9 @@ Example:
        .notice "A=0"
   .endif
 
+  .diag "WTA/2021-05-07: replace 'redirect' with 'return' after switch to 2.4"
+        http-request redirect location /goaway if ABUSE
+
 
 2.5. Time format
 ----------------
diff --git a/src/cfgparse.c b/src/cfgparse.c
index dead21d8c..af727440b 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -2136,7 +2136,7 @@ int readcfgfile(const char *file)
 			goto next_line;
 		}
 
-		/* .warning/.error/.notice */
+		/* .warning/.error/.notice/.diag */
 		if (*args[0] == '.') {
 			if (strcmp(args[0], ".alert") == 0) {
 				ha_alert("parsing [%s:%d]: '%s'.\n", file, linenum, args[1]);
@@ -2152,6 +2152,10 @@ int readcfgfile(const char *file)
 				ha_notice("parsing [%s:%d]: '%s'.\n", file, linenum, args[1]);
 				goto next_line;
 			}
+			else if (strcmp(args[0], ".diag") == 0) {
+				ha_diag_warning("parsing [%s:%d]: '%s'.\n", file, linenum, args[1]);
+				goto next_line;
+			}
 			else {
 				ha_alert("parsing [%s:%d]: unknown directive '%s'.\n", file, linenum, args[0]);
 				err_code |= ERR_ALERT | ERR_FATAL;