diff --git a/tests/string_test.cpp b/tests/string_test.cpp
index 71998d8..d55771c 100644
--- a/tests/string_test.cpp
+++ b/tests/string_test.cpp
@@ -39,7 +39,7 @@
   ASSERT_STREQ("Operation not permitted", strerror(1));
 
   // Invalid.
-  ASSERT_STREQ("Unknown error 4294967295", strerror(-1));
+  ASSERT_STREQ("Unknown error -1", strerror(-1));
   ASSERT_STREQ("Unknown error 1234", strerror(1234));
 }