diff --git a/compiler2/ttcn3/Ttcnstuff.cc b/compiler2/ttcn3/Ttcnstuff.cc
index 6be807e40b1493bb9d7b5627f8fdfdf972f017af..e88dca863ba86cfd31005efd380bcd7c266b920c 100644
--- a/compiler2/ttcn3/Ttcnstuff.cc
+++ b/compiler2/ttcn3/Ttcnstuff.cc
@@ -2068,7 +2068,7 @@ namespace Ttcn {
       return;
     }
 
-    int ABCLength = strlen(ABCClass);
+    size_t ABCLength = strlen(ABCClass);
     if (ABCLength < 3 || ABCLength > 5) {
       // incorrect ABC number
       type_ = NONE;