diff --git a/app/voicemails/voicemail_messages.php b/app/voicemails/voicemail_messages.php
index c0925434b2..a2441f7cc6 100644
--- a/app/voicemails/voicemail_messages.php
+++ b/app/voicemails/voicemail_messages.php
@@ -224,7 +224,7 @@
 	}
 
 //check or uncheck all voicemail checkboxes
-	if (sizeof($vm_msg_ids) > 0) {
+	if (is_array($vm_msg_ids) && sizeof($vm_msg_ids) > 0) {
 		echo "<script>\n";
 		echo "	function check(what, voicemail_id) {\n";
 		foreach ($vm_msg_ids as $voicemail_id => $checkbox_ids) {
@@ -256,4 +256,4 @@
 //include the footer
 	require_once "resources/footer.php";
 
-?>
\ No newline at end of file
+?>