diff --git a/delta_performer.h b/delta_performer.h
index 1356bae..4a096c2 100644
--- a/delta_performer.h
+++ b/delta_performer.h
@@ -30,7 +30,7 @@
 
   // Wrapper around write. Returns bytes written on success or
   // -errno on error.
-  int Write(const void* bytes, size_t count);
+  ssize_t Write(const void* bytes, size_t count);
 
   // Wrapper around close. Returns 0 on success or -errno on error.
   int Close();