diff --git a/configure.ac b/configure.ac
index c9aa37ab..13cbc8c4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -38,7 +38,6 @@ dnl Checks for libraries.
 
 dnl Checks for header files.
 AC_HEADER_DIRENT
-AC_HEADER_STDC
 AC_HEADER_SYS_WAIT
 AC_HEADER_STDBOOL
 
diff --git a/lib/defines.h b/lib/defines.h
index fc1521cb..08483940 100644
--- a/lib/defines.h
+++ b/lib/defines.h
@@ -61,16 +61,8 @@ extern char * textdomain (const char * domainname);
 #endif
 #endif
 
-#if STDC_HEADERS
-# include <stdlib.h>
-# include <string.h>
-#else				/* not STDC_HEADERS */
-# ifndef HAVE_STRCHR
-#  define strchr index
-#  define strrchr rindex
-# endif
-char *strchr (), *strrchr (), *strtok ();
-#endif				/* not STDC_HEADERS */
+#include <stdlib.h>
+#include <string.h>
 
 #if HAVE_ERRNO_H
 # include <errno.h>
diff --git a/libmisc/getdate.y b/libmisc/getdate.y
index 7afa995b..9b9f48c2 100644
--- a/libmisc/getdate.y
+++ b/libmisc/getdate.y
@@ -31,11 +31,7 @@
 #include <ctype.h>
 #include <time.h>
 
-#if defined (STDC_HEADERS) || (!defined (isascii) && !defined (HAVE_ISASCII))
-# define IN_CTYPE_DOMAIN(c) 1
-#else
-# define IN_CTYPE_DOMAIN(c) isascii(c)
-#endif
+#define IN_CTYPE_DOMAIN(c) 1
 
 #define ISSPACE(c) (IN_CTYPE_DOMAIN (c) && isspace (c))
 #define ISALPHA(c) (IN_CTYPE_DOMAIN (c) && isalpha (c))
@@ -54,9 +50,7 @@
 
 #include "getdate.h"
 
-#if defined (STDC_HEADERS)
-# include <string.h>
-#endif
+#include <string.h>
 
 /* Some old versions of bison generate parsers that use bcopy.
    That loses on systems that don't provide the function, so we have