diff --git a/include/_tail_cc/sys/stdtypes.h b/include/_tail_cc/sys/stdtypes.h
index 78e6c06f..202bfe8e 100644
--- a/include/_tail_cc/sys/stdtypes.h
+++ b/include/_tail_cc/sys/stdtypes.h
@@ -9,9 +9,11 @@
 #define	__STDTYPES_H__
 
 typedef long	sigset_t;	/* for <signal.h> on SUN's */
+#ifndef __STDC__
 typedef	long	time_t;
 typedef	long	size_t;
 typedef long	clock_t;
+#endif
 typedef int	pid_t;
 typedef unsigned short	gid_t;
 typedef unsigned short	uid_t;
diff --git a/include/_tail_cc/sys/types.h b/include/_tail_cc/sys/types.h
index 8dcf84ec..71491686 100644
--- a/include/_tail_cc/sys/types.h
+++ b/include/_tail_cc/sys/types.h
@@ -4,9 +4,6 @@
  * See the copyright notice in the ACK home directory, in the file "Copyright".
  */
 
-#ifndef __TYPES_H__
-#define __TYPES_H__
-
 /*
  * Basic system types and major/minor device constructing/busting macros.
  */
@@ -14,6 +11,7 @@
 #if     !defined(_SYS_TYPES_H)
 #define _SYS_TYPES_H
 
+#ifdef __STDC__
 #if     !defined(_SIZE_T)
 #define _SIZE_T
 typedef unsigned int    size_t;         /* type returned by sizeof */
@@ -23,6 +21,7 @@ typedef unsigned int    size_t;         /* type returned by sizeof */
 #define _TIME_T
 typedef unsigned long   time_t;
 #endif  /* TIME_T */
+#endif
 
 #if !defined(_POSIX_SOURCE)
 
@@ -77,4 +76,4 @@ typedef unsigned short  uid_t;  /* user id */
 #endif  /* _MINIX */
 #endif  /* _POSIX_SOURCE */
 
-#endif /* __TYPES_H__ */
+#endif /* _SYS_TYPES_H */
diff --git a/include/_tail_mon/sys/types.h b/include/_tail_mon/sys/types.h
index 8dcf84ec..71491686 100644
--- a/include/_tail_mon/sys/types.h
+++ b/include/_tail_mon/sys/types.h
@@ -4,9 +4,6 @@
  * See the copyright notice in the ACK home directory, in the file "Copyright".
  */
 
-#ifndef __TYPES_H__
-#define __TYPES_H__
-
 /*
  * Basic system types and major/minor device constructing/busting macros.
  */
@@ -14,6 +11,7 @@
 #if     !defined(_SYS_TYPES_H)
 #define _SYS_TYPES_H
 
+#ifdef __STDC__
 #if     !defined(_SIZE_T)
 #define _SIZE_T
 typedef unsigned int    size_t;         /* type returned by sizeof */
@@ -23,6 +21,7 @@ typedef unsigned int    size_t;         /* type returned by sizeof */
 #define _TIME_T
 typedef unsigned long   time_t;
 #endif  /* TIME_T */
+#endif
 
 #if !defined(_POSIX_SOURCE)
 
@@ -77,4 +76,4 @@ typedef unsigned short  uid_t;  /* user id */
 #endif  /* _MINIX */
 #endif  /* _POSIX_SOURCE */
 
-#endif /* __TYPES_H__ */
+#endif /* _SYS_TYPES_H */