diff --git a/libc/test/src/stdlib/strtoul_test.cpp b/libc/test/src/stdlib/strtoul_test.cpp
--- a/libc/test/src/stdlib/strtoul_test.cpp
+++ b/libc/test/src/stdlib/strtoul_test.cpp
@@ -227,7 +227,7 @@
             } else {
               errno = 0;
               ASSERT_EQ(__llvm_libc::strtoul(small_string, nullptr, base),
-                        first_digit);
+                        static_cast<unsigned long int>(first_digit));
               ASSERT_EQ(errno, 0);
             }
           } else {