diff --git a/tests/string_test.cpp b/tests/string_test.cpp
index 3f7d500..08c73a1 100644
--- a/tests/string_test.cpp
+++ b/tests/string_test.cpp
@@ -77,7 +77,7 @@
 
   // Invalid.
   ASSERT_EQ(0, strerror_r(-1, buf, sizeof(buf)));
-  ASSERT_STREQ("Unknown error 4294967295", buf);
+  ASSERT_STREQ("Unknown error -1", buf);
   ASSERT_EQ(0, strerror_r(1234, buf, sizeof(buf)));
   ASSERT_STREQ("Unknown error 1234", buf);