diff --git a/kitty/data-types.h b/kitty/data-types.h
index 6345a2d6e..0eb47bdc2 100644
--- a/kitty/data-types.h
+++ b/kitty/data-types.h
@@ -7,8 +7,12 @@
 
 #pragma once
 
+#ifdef _POSIX_C_SOURCE
+#error "Must include \"data-types.h\" before any system headers"
+#endif
 #define PY_SSIZE_T_CLEAN
 #include <Python.h>
+
 #include <assert.h>
 #include <stdint.h>
 #include <stdbool.h>
diff --git a/kitty/launcher/main.c b/kitty/launcher/main.c
index 4077a8080..133ce76e8 100644
--- a/kitty/launcher/main.c
+++ b/kitty/launcher/main.c
@@ -6,6 +6,8 @@
  */
 
 #define PY_SSIZE_T_CLEAN
+#include <Python.h>
+
 #include <libgen.h>
 #ifdef __APPLE__
 #include <mach-o/dyld.h>
@@ -18,7 +20,6 @@
 #include <stdint.h>
 #include <string.h>
 #include <wchar.h>
-#include <Python.h>
 #include <fcntl.h>
 #include "launcher.h"
 
diff --git a/kitty/launcher/single-instance.c b/kitty/launcher/single-instance.c
index 0e06a804c..a12ebbf03 100644
--- a/kitty/launcher/single-instance.c
+++ b/kitty/launcher/single-instance.c
@@ -5,6 +5,8 @@
  * Distributed under terms of the GPL3 license.
  */
 
+#include "../data-types.h"
+
 #ifdef __APPLE__
 // Needed for _CS_DARWIN_USER_CACHE_DIR
 #define _DARWIN_C_SOURCE
@@ -347,4 +349,3 @@ single_instance_main(int argc, char *argv[], const CLIOptions *opts) {
         else fail_on_errno("Failed to bind single instance socket");
     } else set_single_instance_socket(s);
 }
-
diff --git a/kitty/screen.c b/kitty/screen.c
index 98645c880..52f91b6be 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -10,6 +10,7 @@
     if (PyModule_AddFunctions(module, module_methods) != 0) return false; \
 }
 
+#include "data-types.h"
 #include "control-codes.h"
 #include "state.h"
 #include "iqsort.h"