diff --git a/common/utils_unittest.cc b/common/utils_unittest.cc
index 6c4e5af..24468b9 100644
--- a/common/utils_unittest.cc
+++ b/common/utils_unittest.cc
@@ -413,7 +413,8 @@
   string contents;
   EXPECT_TRUE(utils::ReadFile(path.value(), &contents));
   EXPECT_EQ(contents, expected_contents);
-  EXPECT_EQ(utils::FileSize(path.value()), expected_contents.size());
+  EXPECT_EQ(static_cast<off_t>(expected_contents.size()),
+            utils::FileSize(path.value()));
 }
 
 TEST(UtilsTest, ConvertToOmahaInstallDate) {