diff --git a/include/stdint.h b/include/stdint.h
index 81f88d59..b306fa67 100644
--- a/include/stdint.h
+++ b/include/stdint.h
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2017 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2017,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  * Copyright © 2018 Peter De Wachter <pdewacht@gmail.com>
  *
  * This file is part of GNU Mes.
@@ -55,8 +55,10 @@ typedef unsigned short uint16_t;
 typedef short int16_t;
 typedef unsigned uint32_t;
 typedef int int32_t;
+#if __SIZEOF_LONG_LONG__
 typedef unsigned long long uint64_t;
 typedef long long int64_t;
+#endif // __SIZEOF_LONG_LONG__
 
 typedef int intmax_t;
 typedef unsigned uintmax_t;
diff --git a/module/mescc/mescc.scm b/module/mescc/mescc.scm
index 6f334945..518e4b33 100644
--- a/module/mescc/mescc.scm
+++ b/module/mescc/mescc.scm
@@ -23,6 +23,7 @@
   #:use-module (ice-9 getopt-long)
   #:use-module (mes misc)
 
+  #:use-module (mescc info)
   #:use-module (mescc armv4 info)
   #:use-module (mescc i386 info)
   #:use-module (mescc x86_64 info)
@@ -59,7 +60,7 @@
          (prefix (option-ref options 'prefix ""))
          (machine (option-ref options 'machine "32"))
          (arch (arch-get options))
-         (defines (cons (arch-get-define options) defines))
+         (defines (append (arch-get-defines options) defines))
          (verbose? (count-opt options 'verbose)))
     (with-output-to-file ast-file-name
       (lambda _ (for-each (cut c->ast prefix defines includes arch pretty-print/write verbose? <>) files)))))
@@ -96,7 +97,7 @@
          (includes (cons (option-ref options 'includedir #f) includes))
          (includes (cons dir includes))
          (prefix (option-ref options 'prefix ""))
-         (defines (cons (arch-get-define options) defines))
+         (defines (append (arch-get-defines options) defines))
          (arch (arch-get options))
          (verbose? (count-opt options 'verbose)))
     (with-input-from-file file-name
@@ -326,11 +327,25 @@
           ((equal? arch "x86") (x86-info))
           ((equal? arch "x86_64") (x86_64-info)))))
 
-(define (arch-get-define options)
-  (let ((arch (arch-get options)))
-    (cond ((equal? arch "arm") "__arm__=1")
-          ((equal? arch "x86") "__i386__=1")
-          ((equal? arch "x86_64") "__x86_64__=1"))))
+(define (arch-get-defines options)
+  (let* ((arch (arch-get options))
+         (info (arch-get-info options))
+         (types (.types info)))
+    (define (sizeof type)
+      (type:size (assoc-ref types type)))
+    (let ((int (sizeof "int"))
+          (long (sizeof "long"))
+          (long-long (sizeof "long long")))
+      (cons (cond ((equal? arch "arm")
+                   "__arm__=1")
+                  ((equal? arch "x86")
+                   "__i386__=1")
+                  ((equal? arch "x86_64")
+                   "__x86_64__=1"))
+            `(,(string-append "__SIZEOF_INT__=" (number->string int))
+              ,(string-append "__SIZEOF_LONG__=" (number->string long))
+              ,@(if (< long-long 8) '() ;C99: long long must be >= 8
+                    '("__SIZEOF_LONG_LONG__=8")))))))
 
 (define (arch-get-machine options)
   (let* ((machine (option-ref options 'machine #f))