Index: uspace/lib/c/generic/thread/tls.c
===================================================================
--- uspace/lib/c/generic/thread/tls.c	(revision d8cb48d0d5ff99e259bd58c8606fc402434818ea)
+++ uspace/lib/c/generic/thread/tls.c	(revision ce52c333dd9013cd4e9c22121ab41c36aee9c7d4)
@@ -37,4 +37,5 @@
 
 #include <assert.h>
+#include <stdalign.h>
 #include <stddef.h>
 #include <align.h>
@@ -69,5 +70,5 @@
 #else
 	size_t tls_size = tls ? tls->p_memsz : 0;
-	return -ALIGN_UP((ptrdiff_t) tls_size, max(tls_align, _Alignof(tcb_t)));
+	return -ALIGN_UP((ptrdiff_t) tls_size, max(tls_align, alignof(tcb_t)));
 #endif
 }
@@ -104,8 +105,8 @@
 #else
 	size_t alloc_size =
-	    ALIGN_UP(tls_size, max(tls_align, _Alignof(tcb_t))) + sizeof(tcb_t);
-#endif
-
-	void *area = alloc(max(tls_align, _Alignof(tcb_t)), alloc_size);
+	    ALIGN_UP(tls_size, max(tls_align, alignof(tcb_t))) + sizeof(tcb_t);
+#endif
+
+	void *area = alloc(max(tls_align, alignof(tcb_t)), alloc_size);
 	if (!area)
 		return NULL;
@@ -187,5 +188,5 @@
 	tls_free_arch(tcb,
 	    ALIGN_UP(tls->p_memsz, tls->p_align) + sizeof(tcb_t),
-	    max(tls->p_align, _Alignof(tcb_t)));
+	    max(tls->p_align, alignof(tcb_t)));
 }