diff --git a/CHANGES b/CHANGES
index bd9b01a1fa..fb6684b136 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+6213.	[bug]		Mark a primary server as temporarily unreachable if the
+			TCP connection attempt times out. [GL #4215]
+
 6212.	[placeholder]
 
 6211.	[func]		Remove 'auto-dnssec'. This obsoletes the configuration
diff --git a/lib/dns/xfrin.c b/lib/dns/xfrin.c
index bf3460169a..b144c46663 100644
--- a/lib/dns/xfrin.c
+++ b/lib/dns/xfrin.c
@@ -1057,9 +1057,11 @@ failure:
 	case ISC_R_NETUNREACH:
 	case ISC_R_HOSTUNREACH:
 	case ISC_R_CONNREFUSED:
+	case ISC_R_TIMEDOUT:
 		/*
-		 * Add the server to unreachable primaries table only if
-		 * the server has a permanent networking error.
+		 * Add the server to unreachable primaries table if
+		 * the server has a permanent networking error or
+		 * the connection attempt as timed out.
 		 */
 		zmgr = dns_zone_getmgr(xfr->zone);
 		if (zmgr != NULL) {