diff --git a/grc/gsm_block_tree.xml b/grc/gsm_block_tree.xml
index 2503710..5837ce2 100644
--- a/grc/gsm_block_tree.xml
+++ b/grc/gsm_block_tree.xml
@@ -51,6 +51,7 @@
       <block>gsm_message_printer</block>
       <block>gsm_clock_offset_corrector</block>
       <block>gsm_tmsi_dumper</block>
+      <block>gsm_message_source</block>
     </cat>
   </cat>
 </cat>