diff --git a/Client.cpp b/Client.cpp
index 13918e91..acef5e7e 100644
--- a/Client.cpp
+++ b/Client.cpp
@@ -180,7 +180,10 @@ void CClient::ReadLine(const CString& sData) {
 	} else if (sCommand.Equals("PING")) {
 		// All PONGs are generated by znc. We will still forward this to
 		// the ircd, but all PONGs from irc will be blocked.
-		PutClient(":irc.znc.in PONG irc.znc.in " + sLine.substr(5));
+		if (sLine.length() >= 5)
+			PutClient(":irc.znc.in PONG irc.znc.in " + sLine.substr(5));
+		else
+			PutClient(":irc.znc.in PONG irc.znc.in");
 	} else if (sCommand.Equals("PONG")) {
 		// Block PONGs, we already responded to the pings
 		return;