diff --git a/src/basicio.cpp b/src/basicio.cpp
index ae3e35b3..373d7c9c 100644
--- a/src/basicio.cpp
+++ b/src/basicio.cpp
@@ -488,7 +488,7 @@ size_t FileIo::size() const {
   int ret = p_->stat(buf);
 
   if (ret != 0)
-    return -1;
+    return std::numeric_limits<size_t>::max();
   return buf.st_size;
 }