diff --git a/sys/libc/include/endian.h b/sys/libc/include/endian.h
index ca90d3b128..d4a8de3866 100644
--- a/sys/libc/include/endian.h
+++ b/sys/libc/include/endian.h
@@ -30,17 +30,17 @@ extern "C" {
 /**
  * @brief   A numeric constant representing little endian byte order
  */
-#define LITTLE_ENDIAN   implementation_defined
+#define LITTLE_ENDIAN   magic-number
 
 /**
  * @brief   A numeric constant representing big endian byte order
  */
-#define BIG_ENDIAN      implementation_defined
+#define BIG_ENDIAN      magic-number
 
 /**
  * @brief   A numeric constant representing PDP endian byte order
  */
-#define PDP_ENDIAN      implementation_defined
+#define PDP_ENDIAN      magic-number
 
 /**
  * @brief   The byte order of this machines indicated by the constant
@@ -69,10 +69,10 @@ uint64_t le64toh(uint64_t little_endian_64bits);/**< little endian to host, 64 b
 
 #else /* DOXYGEN */
 
-#define LITTLE_ENDIAN   _LITTLE_ENDIAN
-#define BIG_ENDIAN      _BIG_ENDIAN
-#define PDP_ENDIAN      _PDP_ENDIAN
-#define BYTE_ORDER      _BYTE_ORDER
+#define LITTLE_ENDIAN   1234
+#define BIG_ENDIAN      4321
+#define PDP_ENDIAN      3412
+#define BYTE_ORDER      __BYTE_ORDER__
 
 #if BYTE_ORDER == LITTLE_ENDIAN
 #  define htobe16(_x) __builtin_bswap16(_x)
diff --git a/tests/unittests/tests-libc/tests-libc.c b/tests/unittests/tests-libc/tests-libc.c
index 82796c312c..9fa8f10c20 100644
--- a/tests/unittests/tests-libc/tests-libc.c
+++ b/tests/unittests/tests-libc/tests-libc.c
@@ -89,6 +89,11 @@ static void test_libc_endian(void)
     TEST_ASSERT_EQUAL_INT(le32toh(u32_le.as_number), u32_host);
     TEST_ASSERT_EQUAL_INT(be64toh(u64_be.as_number), u64_host);
     TEST_ASSERT_EQUAL_INT(le64toh(u64_le.as_number), u64_host);
+
+    /* check that magic numbers in the constants are what is commonly expected */
+    TEST_ASSERT_EQUAL_INT(LITTLE_ENDIAN, 1234);
+    TEST_ASSERT_EQUAL_INT(BIG_ENDIAN, 4321);
+    TEST_ASSERT_EQUAL_INT(PDP_ENDIAN, 3412);
 }
 /** @} */