diff --git a/apps/app_sendtext.c b/apps/app_sendtext.c
index 91273b45ac..f890ae4bfb 100644
--- a/apps/app_sendtext.c
+++ b/apps/app_sendtext.c
@@ -81,7 +81,9 @@ static int sendtext_exec(struct ast_channel *chan, void *data)
 		AST_APP_ARG(text);
 	);
 
-	if (ast_strlen_zero(data)) {
+	/* NOT ast_strlen_zero, because some protocols (e.g. SIP) MUST be able to
+	 * send a zero-length message. */
+	if (!data) {
 		ast_log(LOG_WARNING, "SendText requires an argument (text)\n");
 		return -1;
 	} else
diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index c255f5edc2..30a0e73dae 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -4187,7 +4187,9 @@ static int sip_sendtext(struct ast_channel *ast, const char *text)
 		ast_verbose("Sending text %s on %s\n", text, ast->name);
 	if (!p)
 		return -1;
-	if (ast_strlen_zero(text))
+	/* NOT ast_strlen_zero, because a zero-length message is specifically
+	 * allowed by RFC 3428 (See section 10, Examples) */
+	if (!text)
 		return 0;
 	if (debug)
 		ast_verbose("Really sending text %s on %s\n", text, ast->name);