diff --git a/src/Coherence/Config/cache-config.xsd b/src/Coherence/Config/cache-config.xsd
index f6ff1b0..18f7472 100644
--- a/src/Coherence/Config/cache-config.xsd
+++ b/src/Coherence/Config/cache-config.xsd
@@ -1007,6 +1007,12 @@
 
         If the value does not contain a unit, a unit of milliseconds is assumed.
 
+        The value must be less than or equal to the heartbeat-interval
+        value. If a larger value is specified, the heartbeat-interval
+        value will be used.
+
+        The default value is the request-timeout value.
+
         Ping requests are disabled by default.
 
         Used in: outgoing-message-handler