diff --git a/generate.py b/generate.py
index 0f47f97..39597f0 100755
--- a/generate.py
+++ b/generate.py
@@ -86,7 +86,8 @@ def open_and_format(filename):
     with redirect_stdout(f):
         CSyscallsGenerator(
             naming=CNaming('cloudabi_'),
-            header_guard='CLOUDABI_SYSCALLS_H').generate_abi(abi)
+            header_guard='CLOUDABI_SYSCALLS_H',
+            preamble='#include "cloudabi_types.h"\n').generate_abi(abi)
 
 with open('headers/cloudabi_syscalls_info.h', 'w') as f:
     with redirect_stdout(f):
diff --git a/headers/cloudabi_syscalls.h b/headers/cloudabi_syscalls.h
index 199c5e7..be1e4da 100644
--- a/headers/cloudabi_syscalls.h
+++ b/headers/cloudabi_syscalls.h
@@ -28,6 +28,8 @@
 #ifndef CLOUDABI_SYSCALLS_H
 #define CLOUDABI_SYSCALLS_H
 
+#include "cloudabi_types.h"
+
 cloudabi_errno_t cloudabi_sys_clock_res_get(cloudabi_clockid_t clock_id,
                                             cloudabi_timestamp_t *resolution);