diff --git a/cmd-choose-client.c b/cmd-choose-client.c
index 59a5bd27..dd09fe51 100644
--- a/cmd-choose-client.c
+++ b/cmd-choose-client.c
@@ -18,6 +18,8 @@
 
 #include <sys/types.h>
 
+#include <ctype.h>
+
 #include "tmux.h"
 
 /*
diff --git a/cmd-choose-session.c b/cmd-choose-session.c
index 3028df22..87b3437b 100644
--- a/cmd-choose-session.c
+++ b/cmd-choose-session.c
@@ -18,6 +18,8 @@
 
 #include <sys/types.h>
 
+#include <ctype.h>
+
 #include "tmux.h"
 
 /*
diff --git a/cmd-choose-window.c b/cmd-choose-window.c
index ec6b2499..ddc8ecb6 100644
--- a/cmd-choose-window.c
+++ b/cmd-choose-window.c
@@ -18,6 +18,8 @@
 
 #include <sys/types.h>
 
+#include <ctype.h>
+
 #include "tmux.h"
 
 /*