diff --git a/include/zipr_plugin.h b/include/zipr_plugin.h
index 1e463d894fb74cc5b1279b4b6f3cb2f61a79563b..cda34659ecb6698a396766c3e2202d8387d05522 100644
--- a/include/zipr_plugin.h
+++ b/include/zipr_plugin.h
@@ -41,7 +41,7 @@ class ZiprPluginInterface_t
 		{
 			return false;
 		}
-		virtual int WorstCaseInsnSize(libIRDB::Instruction_t*, Zipr_t *)
+		virtual size_t WorstCaseInsnSize(libIRDB::Instruction_t*, Zipr_t *)
 		{
 			return 0;
 		}