diff --git a/ext/f2c_libs/err.c b/ext/f2c_libs/err.c
index d93e80d05..18de588d2 100644
--- a/ext/f2c_libs/err.c
+++ b/ext/f2c_libs/err.c
@@ -10,6 +10,15 @@ extern char *malloc();
 #endif
 #include "fio.h"
 #include "fmt.h"	/* for struct syl */
+
+#ifndef NON_POSIX_STDIO
+#ifdef MSDOS
+#include "io.h"
+#else
+#include "unistd.h"     /* for access */
+#endif
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/ext/f2c_libs/util.c b/ext/f2c_libs/util.c
index f4b3aef2c..09009816b 100644
--- a/ext/f2c_libs/util.c
+++ b/ext/f2c_libs/util.c
@@ -1,6 +1,21 @@
 #include "sysdep1.h"	/* here to get stat64 on some badly designed Linux systems */
 #include "f2c.h"
 #include "fio.h"
+#ifndef KR_headers
+#undef abs
+#undef min
+#undef max
+#include <stdlib.h>
+#endif
+
+#ifndef NON_POSIX_STDIO
+#ifdef MSDOS
+#include "io.h"
+#else
+#include "unistd.h"     /* for access */
+#endif
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif