diff --git a/client.c b/client.c
index 7d524204..7624e7db 100644
--- a/client.c
+++ b/client.c
@@ -25,6 +25,8 @@
 #include "version.h"
 #include "xmalloc.h"
 
+extern char **environ;
+
 struct string {
     size_t len;
     char *str;
diff --git a/slave.c b/slave.c
index 4e8610ce..dc4a8bc6 100644
--- a/slave.c
+++ b/slave.c
@@ -23,6 +23,8 @@
 #include "tokenize.h"
 #include "xmalloc.h"
 
+extern char **environ;
+
 static bool
 is_valid_shell(const char *shell)
 {