diff --git a/cmd-string.c b/cmd-string.c
index 1e471081..a5c5dd12 100644
--- a/cmd-string.c
+++ b/cmd-string.c
@@ -63,7 +63,7 @@ cmd_string_parse(const char *s, struct cmd_list **cmdlist, char **cause)
 	if ((t = strchr(s, ' ')) == NULL && (t = strchr(s, '\t')) == NULL)
 		t = strchr(s, '\0');
 	if ((u = strchr(s, '=')) != NULL && u < t) {
-		if (putenv((char *) s) != 0) {
+		if (putenv(xstrdup(s)) != 0) {
 			xasprintf(cause, "assignment failed: %s", s);
 			return (-1);
 		}
diff --git a/window.c b/window.c
index 06733201..aeed4bc9 100644
--- a/window.c
+++ b/window.c
@@ -473,7 +473,7 @@ window_pane_spawn(struct window_pane *wp,
 		if (chdir(wp->cwd) != 0)
 			chdir("/");
 		for (envq = envp; *envq != NULL; envq++) {
-			if (putenv((char *) *envq) != 0)
+			if (putenv(xstrdup(*envq)) != 0)
 				fatal("putenv failed");
 		}
 		sigreset();