diff --git a/test/unittest/writertest.cpp b/test/unittest/writertest.cpp
index 1025f9f..d189fa1 100644
--- a/test/unittest/writertest.cpp
+++ b/test/unittest/writertest.cpp
@@ -132,7 +132,7 @@ public:
 
 	Ch Peek() const { assert(false); return '\0'; }
 	Ch Take() { assert(false); return '\0'; }
-	size_t Tell() const {  }
+	size_t Tell() const { return 0; }
 
 	Ch* PutBegin() { assert(false); return 0; }
 	void Put(Ch c) { os_.put(c); }