diff --git a/compat/forkpty-sunos.c b/compat/forkpty-sunos.c
index 90452f8d..7b254d82 100644
--- a/compat/forkpty-sunos.c
+++ b/compat/forkpty-sunos.c
@@ -21,6 +21,7 @@
 
 #include <fcntl.h>
 #include <stdlib.h>
+#include <strings.h>
 #include <stropts.h>
 #include <unistd.h>
 
diff --git a/compat/imsg-buffer.c b/compat/imsg-buffer.c
index 24db311d..2ddf0f77 100644
--- a/compat/imsg-buffer.c
+++ b/compat/imsg-buffer.c
@@ -24,6 +24,7 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 
 #include "tmux.h"
diff --git a/compat/imsg.c b/compat/imsg.c
index 0feff660..c4dd191d 100644
--- a/compat/imsg.c
+++ b/compat/imsg.c
@@ -24,6 +24,7 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 
 #include "tmux.h"