diff --git a/Lib/test/test_grp.py b/Lib/test/test_grp.py
index 08958ba..a8dcb63 100755
--- a/Lib/test/test_grp.py
+++ b/Lib/test/test_grp.py
@@ -25,6 +25,9 @@
         for e in entries:
             self.check_value(e)
 
+        if len(entries) > 1000:  # Huge group file (NIS?) -- skip the rest
+            return
+
         for e in entries:
             e2 = grp.getgrgid(e.gr_gid)
             self.check_value(e2)
diff --git a/Lib/test/test_pwd.py b/Lib/test/test_pwd.py
index 12d2bc9..74ce947 100644
--- a/Lib/test/test_pwd.py
+++ b/Lib/test/test_pwd.py
@@ -35,6 +35,9 @@
             entriesbyname.setdefault(e.pw_name, []).append(e)
             entriesbyuid.setdefault(e.pw_uid, []).append(e)
 
+        if len(entries) > 1000:  # Huge passwd file (NIS?) -- skip the rest
+            return
+
         # check whether the entry returned by getpwuid()
         # for each uid is among those from getpwall() for this uid
         for e in entries: