diff --git a/tests/src/test_common.h b/tests/src/test_common.h
index c5cce8241..7053fec64 100644
--- a/tests/src/test_common.h
+++ b/tests/src/test_common.h
@@ -14,6 +14,18 @@
 #ifndef TEST_TEST_COMMON_H
 #define TEST_TEST_COMMON_H
 
+#if !defined(_POSIX_C_SOURCE)
+/* For standards-compliant access to
+ * clock_gettime(), gmtime_r(), ...
+ */
+#define _POSIX_C_SOURCE 200112L
+#endif
+
+/* With GNU libc, define all the things, even when compiling with -pedantic. */
+#if !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
 /* On Mingw-w64, force the use of a C99-compliant printf() and friends.
  * This is necessary on older versions of Mingw and/or Windows runtimes
  * where snprintf does not always zero-terminate the buffer, and does