diff --git a/tests/config.h.in b/tests/config.h.in
index 57c2bd1..5943c07 100644
--- a/tests/config.h.in
+++ b/tests/config.h.in
@@ -14,8 +14,6 @@
 #ifndef LYTEST_CONFIG_H_
 #define LYTEST_CONFIG_H_
 
-#define _GNU_SOURCE
-
 #define UNUSED(x) @COMPILER_UNUSED_ATTR@
 
 #define TESTS_SRC "@CMAKE_CURRENT_SOURCE_DIR@"