diff --git a/grc/misc_utils/gsm_message_printer.xml b/grc/misc_utils/gsm_message_printer.xml
index 8e0a68d..8b44b22 100644
--- a/grc/misc_utils/gsm_message_printer.xml
+++ b/grc/misc_utils/gsm_message_printer.xml
@@ -3,7 +3,16 @@
   <name>Message printer</name>
   <key>gsm_message_printer</key>
   <import>import grgsm</import>
-  <make>grgsm.message_printer()</make>
+  <import>import pmt</import>
+  <make>grgsm.message_printer(pmt.intern($prepend_string))</make>
+
+  <param>
+    <name>Prepend String</name>
+    <key>prepend_string</key>
+    <value></value>
+    <type>string</type>
+    <hide>part</hide>
+  </param>
 
   <sink>
     <name>msgs</name>