diff --git a/app/src/sys/unix/command.c b/app/src/sys/unix/command.c
index 64a54e71..3c2f587d 100644
--- a/app/src/sys/unix/command.c
+++ b/app/src/sys/unix/command.c
@@ -1,6 +1,6 @@
-// for portability
-#define _POSIX_SOURCE // for kill()
-#define _BSD_SOURCE // for readlink()
+// for portability (kill, readlink, strdup, strtok_r)
+#define _POSIX_C_SOURCE 200809L
+#define _BSD_SOURCE
 
 // modern glibc will complain without this
 #define _DEFAULT_SOURCE