diff --git a/include/cia/sync.h b/include/cia/sync.h
new file mode 100644
index 0000000..58336ac
--- /dev/null
+++ b/include/cia/sync.h
@@ -0,0 +1,4 @@
+
+#pragma once
+
+
diff --git a/include/stdatomic.h b/include/stdatomic.h
new file mode 100644
index 0000000..bda28ec
--- /dev/null
+++ b/include/stdatomic.h
@@ -0,0 +1,13 @@
+
+#pragma once
+
+#include <wchar.h>
+#include <stddef.h>
+
+#if defined(__has_include_next)
+    #if __has_include_next(<stdatomic.h>)
+        #include_next <stdatomic.h>
+    #else
+        #define __STDC_NO_ATOMICS__
+    #endif
+#endif
diff --git a/include/stddef.h b/include/stddef.h
index 8e6f00e..2a7ab5b 100644
--- a/include/stddef.h
+++ b/include/stddef.h
@@ -4,6 +4,7 @@
 #include <cia/def.h>
 
 typedef u64 size_t;
+typedef i64 ptrdiff_t;
 
 #if !defined(NULL)
     #define NULL ((void *)0)
diff --git a/include/wchar.h b/include/wchar.h
new file mode 100644
index 0000000..6bde1bc
--- /dev/null
+++ b/include/wchar.h
@@ -0,0 +1,4 @@
+
+#pragma once
+
+typedef u32 wchar_t;
diff --git a/readme.md b/readme.md
index 668e9b2..8ef6372 100644
--- a/readme.md
+++ b/readme.md
@@ -51,7 +51,7 @@ time is discouraged.
 | <signal.h>      | Signal handling.                     | none        |
 | <stdalign.h>    | Alignment.                           | none        |
 | <stdarg.h>      | Variable arguments.                  | none        |
-| <stdatomic.h>   | Atomics.                             | none        |
+| <stdatomic.h>   | Atomics.                             | [1]         |
 | <stdbit.h>      | Bit and byte utilities               | none        |
 | <stdbool.h>     | Boolean type and values.             | none        |
 | <stddef.h>      | Common definitions.                  | none        |
diff --git a/tests/threaded.c b/tests/threaded.c
index 67f3f54..f34fe5c 100644
--- a/tests/threaded.c
+++ b/tests/threaded.c
@@ -2,6 +2,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <threads.h>
+#include <stdatomic.h>
 
 static void print_string_n(char *str, u64 len) {
     fwrite(str, 1, len, stdout);
@@ -32,7 +33,7 @@ static void print_int(i64 number) {
     print_string(p);
 }
 
-volatile i64 counter = 0;
+volatile _Atomic i64 counter = 0;
 
 int thrd_func(void *arg) {
     print_string("child thread: ok!\n");