diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -360,7 +360,7 @@ def andset(repo, subset, x, y):
 
 def orset(repo, subset, x, y):
     xl = getset(repo, subset, x)
-    yl = getset(repo, subset - xl, y)
+    yl = getset(repo, subset, y)
     return xl + yl
 
 def notset(repo, subset, x):
diff --git a/tests/test-revset.t b/tests/test-revset.t
--- a/tests/test-revset.t
+++ b/tests/test-revset.t
@@ -889,9 +889,7 @@ test that `or` operation skips duplicate
   * set:
   <addset
     <baseset [5, 3, 1]>,
-    <filteredset
-      <filteredset
-        <fullreposet+ 0:9>>>>
+    <generatorset+>>
   5
   3
   1
@@ -913,8 +911,7 @@ test that `or` operation skips duplicate
   * set:
   <addset+
     <generatorset+>,
-    <filteredset
-      <baseset [5, 3, 1]>>>
+    <baseset [5, 3, 1]>>
   0
   1
   2
@@ -1432,8 +1429,7 @@ far away.
   <addset
     <baseset [9]>,
     <filteredset
-      <filteredset
-        <fullreposet+ 0:9>>>>
+      <fullreposet+ 0:9>>>
   9
 
   $ try 'd(2:5)'