diff --git a/libkeke_array.c b/libkeke_array.c
index 935633b..371f5cc 100644
--- a/libkeke_array.c
+++ b/libkeke_array.c
@@ -1,6 +1,9 @@
 #ifndef LIBKEKE_ARRAY
 #define LIBKEKE_ARRAY
 
+// Required for qsort_r on Linux
+#define _GNU_SOURCE
+
 #include <stddef.h>
 #include <stdlib.h>
 #include <stdint.h>