diff --git a/src/libstore/sandbox-defaults.sb.in b/src/libstore/sandbox-defaults.sb.in
index 12c39fa7f217adafd2f16ec82882d7a1136201c6..702f05602bd0e9a357579d905f87f8fc3f52407e 100644
--- a/src/libstore/sandbox-defaults.sb.in
+++ b/src/libstore/sandbox-defaults.sb.in
@@ -35,7 +35,10 @@
        (literal "/private/var/run/resolv.conf"))
 
 ; some builders use filehandles other than stdin/stdout
-(allow file* (subpath "/dev/fd"))
+(allow file*
+        (subpath "/dev/fd")
+        (literal "/dev/ptmx")
+        (regex #"^/dev/[pt]ty.*$"))
 
 ; allow everything inside TMP
 (allow file* process-exec