diff --git a/src/cfgparse-listen.c b/src/cfgparse-listen.c
index 38f2bc4d0..c467e12c4 100644
--- a/src/cfgparse-listen.c
+++ b/src/cfgparse-listen.c
@@ -256,8 +256,15 @@ int cfg_parse_listen_match_option(const char *file, int linenum, int kwm,
 	for (optnum = 0; config_opts[optnum].name; optnum++) {
 		if (strcmp(args[1], config_opts[optnum].name) == 0) {
 			if (config_opts[optnum].cap == PR_CAP_NONE) {
-				ha_alert("parsing [%s:%d]: option '%s' is not supported due to build options.\n",
-					 file, linenum, config_opts[optnum].name);
+				if (config_opts[optnum].val)
+					ha_alert("parsing [%s:%d]: support for option '%s' was removed in version %u.%u.\n",
+					         file, linenum, config_opts[optnum].name,
+					         (config_opts[optnum].val >> 8) & 0xff,
+					         config_opts[optnum].val & 0xff);
+				else
+					ha_alert("parsing [%s:%d]: option '%s' is not supported due to build options.\n",
+					         file, linenum, config_opts[optnum].name);
+
 				*err_code |= ERR_ALERT | ERR_FATAL;
 				goto out;
 			}
diff --git a/src/proxy.c b/src/proxy.c
index ae1b589a4..6b54a08ea 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -94,7 +94,11 @@ struct show_srv_ctx {
 	} state;
 };
 
-/* proxy->options */
+/* proxy->options. For unsupported ones, pass 0 in the "cap" (PR_CAP_*) field.
+ * If this is due to feature removal, the val field can contain the version the
+ * option was removed in the "val" (PR_O_*) field as (major<<8)+minor (e.g.
+ * 0x305 for "3.5"). Pass zero there to indicate build options instead.
+ */
 const struct cfg_opt cfg_opts[] =
 {
 	{ "abortonclose", PR_O_ABRT_CLOSE, PR_CAP_BE|PR_CAP_FE, 0, 0 },