diff --git a/src/util.h b/src/util.h
index 803de5d..41cb35d 100644
--- a/src/util.h
+++ b/src/util.h
@@ -25,10 +25,4 @@ typedef intptr_t ssize_t;
 #define inline __inline
 #endif
 
-/* Polyfill `static_assert` for some versions of clang and gcc. */
-#if (defined(__clang__) || defined(__GNUC__)) && !defined(static_assert)
-#define static_assert(condition, message) typedef __attribute__( \
-    (__unused__)) int __static_assert_##__LINE__[(condition) ? 1 : -1]
-#endif
-
 #endif /* WEPOLL_UTIL_H_ */
diff --git a/test/shared/test-util.h b/test/shared/test-util.h
index 68c9497..458e83b 100644
--- a/test/shared/test-util.h
+++ b/test/shared/test-util.h
@@ -1,6 +1,8 @@
 #ifndef TEST_UTIL_H_
 #define TEST_UTIL_H_
 
+#include <assert.h>
+
 #ifdef __clang__
 #pragma clang diagnostic ignored "-Wbad-function-cast"
 #pragma clang diagnostic ignored "-Wcast-qual"
@@ -33,4 +35,10 @@ void no_inline no_return check_fail(const char* message);
                       "  line: " _check_to_string(__LINE__) "\n"), \
            0))
 
+/* Polyfill `static_assert` for some versions of clang and gcc. */
+#if (defined(__clang__) || defined(__GNUC__)) && !defined(static_assert)
+#define static_assert(condition, message) typedef __attribute__( \
+    (__unused__)) int __static_assert_##__LINE__[(condition) ? 1 : -1]
+#endif
+
 #endif /* TEST_UTIL_H_ */