diff --git a/Modules/readline.c b/Modules/readline.c
index e12ae1d70e9..c74aee08c16 100644
--- a/Modules/readline.c
+++ b/Modules/readline.c
@@ -12,6 +12,10 @@
 #include <signal.h>
 #include <errno.h>
 
+#ifdef HAVE_UNISTD_H
+#include <unistd.h> /* For isatty() */
+#endif
+
 /* GNU readline definitions */
 #include <readline/readline.h> /* You may need to add an -I option to Setup */
 
diff --git a/Python/frozenmain.c b/Python/frozenmain.c
index 10fba54ce94..c823fa1fab8 100644
--- a/Python/frozenmain.c
+++ b/Python/frozenmain.c
@@ -33,6 +33,10 @@ PERFORMANCE OF THIS SOFTWARE.
 
 #include "Python.h"
 
+#ifdef HAVE_UNISTD_H
+#include <unistd.h> /* For isatty() */
+#endif
+
 /* Main program */
 
 int