diff --git a/cpp/protoutils.cc b/cpp/protoutils.cc
index 75c7167..00dd732 100644
--- a/cpp/protoutils.cc
+++ b/cpp/protoutils.cc
@@ -60,6 +60,8 @@ namespace f8
             msgid_enum_name = "cs.SMMessageId_e";
         } else if (msgname[0] == 'S' && msgname[1] == 'S') {
             msgid_enum_name = "ss.SSMessageId_e";
+        } else if (msgname[0] == 'I' && msgname[1] == 'M') {
+            msgid_enum_name = "im.IMMessageId_e";
         #endif
         } else {
             assert(false);