diff --git a/Lib/fontTools/feaLib/builder.py b/Lib/fontTools/feaLib/builder.py
index 05a15173f..9ff49b29e 100644
--- a/Lib/fontTools/feaLib/builder.py
+++ b/Lib/fontTools/feaLib/builder.py
@@ -714,14 +714,7 @@ class LookupBuilder(object):
         return {}
 
     def buildLookup_(self, subtables):
-        lookup = otTables.Lookup()
-        lookup.LookupFlag = self.lookupflag
-        lookup.LookupType = self.lookup_type
-        lookup.SubTable = subtables
-        lookup.SubTableCount = len(subtables)
-        if self.markFilterSet is not None:
-            lookup.MarkFilteringSet = self.markFilterSet
-        return lookup
+        return otl.buildLookup(subtables, self.lookupflag, self.markFilterSet)
 
     def buildMarkClasses_(self, marks):
         """{"cedilla": ("BOTTOM", ast.Anchor), ...} --> {"BOTTOM":0, "TOP":1}
diff --git a/Lib/fontTools/otlLib/builder.py b/Lib/fontTools/otlLib/builder.py
index 01643dcfa..2bbb45186 100644
--- a/Lib/fontTools/otlLib/builder.py
+++ b/Lib/fontTools/otlLib/builder.py
@@ -10,6 +10,37 @@ def buildCoverage(glyphs, glyphMap):
     return self
 
 
+LOOKUP_FLAG_RIGHT_TO_LEFT = 0x0001
+LOOKUP_FLAG_IGNORE_BASE_GLYPHS = 0x0002
+LOOKUP_FLAG_IGNORE_LIGATURES = 0x0004
+LOOKUP_FLAG_IGNORE_MARKS = 0x0008
+LOOKUP_FLAG_USE_MARK_FILTERING_SET = 0x0010
+
+
+def buildLookup(subtables, flags=0, markFilterSet=None):
+    if not subtables:
+        return None
+    assert all(t.LookupType == subtables[0].LookupType for t in subtables), \
+        ("all subtables must have the same LookupType; got %s" %
+         repr([t.LookupType for t in subtables]))
+    self = ot.Lookup()
+    self.LookupType = subtables[0].LookupType
+    self.LookupFlag = flags
+    self.SubTable = subtables
+    self.SubTableCount = len(subtables)
+    if markFilterSet is not None:
+        assert self.LookupFlag & LOOKUP_FLAG_USE_MARK_FILTERING_SET, \
+            ("if markFilterSet is not None, flags must set "
+             "LOOKUP_FLAG_USE_MARK_FILTERING_SET; flags=0x%04x" % flags)
+        assert isinstance(markFilterSet, int), markFilterSet
+        self.MarkFilteringSet = markFilterSet
+    else:
+        assert (self.LookupFlag & LOOKUP_FLAG_USE_MARK_FILTERING_SET) == 0, \
+            ("if markFilterSet is None, flags must not set "
+             "LOOKUP_FLAG_USE_MARK_FILTERING_SET; flags=0x%04x" % flags)
+    return self
+
+
 # GSUB
 
 
diff --git a/Lib/fontTools/otlLib/builder_test.py b/Lib/fontTools/otlLib/builder_test.py
index 3238c71a8..eb7b2eab6 100644
--- a/Lib/fontTools/otlLib/builder_test.py
+++ b/Lib/fontTools/otlLib/builder_test.py
@@ -14,6 +14,13 @@ class BuilderTest(unittest.TestCase):
     ANCHOR2 = builder.buildAnchor(22, -22)
     ANCHOR3 = builder.buildAnchor(33, -33)
 
+    def __init__(self, methodName):
+        unittest.TestCase.__init__(self, methodName)
+        # Python 3 renamed assertRaisesRegexp to assertRaisesRegex,
+        # and fires deprecation warnings if a program uses the old name.
+        if not hasattr(self, "assertRaisesRegex"):
+            self.assertRaisesRegex = self.assertRaisesRegexp
+
     def test_buildAnchor_format1(self):
         anchor = builder.buildAnchor(23, 42)
         self.assertEqual(getXML(anchor.toXML),
@@ -256,6 +263,65 @@ class BuilderTest(unittest.TestCase):
                          '  </CaretValue>'
                          '</LigGlyph>')
 
+    def test_buildLookup(self):
+        s1 = builder.buildSingleSubst({"one": "two"})
+        s2 = builder.buildSingleSubst({"three": "four"})
+        lookup = builder.buildLookup([s1, s2], flags=7)
+        self.assertEqual(getXML(lookup.toXML),
+                         '<Lookup>'
+                         '  <!-- LookupType=1 -->'
+                         '  <LookupFlag value="7"/>'
+                         '  <!-- SubTableCount=2 -->'
+                         '  <SingleSubst index="0">'
+                         '    <Substitution in="one" out="two"/>'
+                         '  </SingleSubst>'
+                         '  <SingleSubst index="1">'
+                         '    <Substitution in="three" out="four"/>'
+                         '  </SingleSubst>'
+                         '</Lookup>')
+
+    def test_buildLookup_badFlags(self):
+        s = builder.buildSingleSubst({"one": "two"})
+        self.assertRaisesRegex(
+            AssertionError, "if markFilterSet is None, "
+            "flags must not set LOOKUP_FLAG_USE_MARK_FILTERING_SET; "
+            "flags=0x0010",
+            builder.buildLookup, [s],
+            builder.LOOKUP_FLAG_USE_MARK_FILTERING_SET, None)
+        self.assertRaisesRegex(
+            AssertionError, "if markFilterSet is not None, "
+            "flags must set LOOKUP_FLAG_USE_MARK_FILTERING_SET; "
+            "flags=0x0004",
+            builder.buildLookup, [s],
+            builder.LOOKUP_FLAG_IGNORE_LIGATURES, 777)
+
+    def test_buildLookup_conflictingSubtableTypes(self):
+        s1 = builder.buildSingleSubst({"one": "two"})
+        s2 = builder.buildAlternateSubst({"one": ["two", "three"]})
+        self.assertRaisesRegex(
+            AssertionError, "all subtables must have the same LookupType",
+            builder.buildLookup, [s1, s2])
+
+    def test_buildLookup_noSubtables(self):
+        self.assertIsNone(builder.buildLookup([]))
+        self.assertIsNone(builder.buildLookup(None))
+
+    def test_buildLookup_markFilterSet(self):
+        s = builder.buildSingleSubst({"one": "two"})
+        flags = (builder.LOOKUP_FLAG_RIGHT_TO_LEFT |
+                 builder.LOOKUP_FLAG_USE_MARK_FILTERING_SET)
+        lookup = builder.buildLookup([s], flags, markFilterSet=999)
+        self.assertEqual(getXML(lookup.toXML),
+                         '<Lookup>'
+                         '  <!-- LookupType=1 -->'
+                         '  <LookupFlag value="17"/>'
+                         '  <!-- SubTableCount=1 -->'
+                         '  <SingleSubst index="0">'
+                         '    <Substitution in="one" out="two"/>'
+                         '  </SingleSubst>'
+                         '  <MarkFilteringSet value="999"/>'
+                         '</Lookup>')
+
     def test_buildMarkGlyphSetsDef(self):
         marksets = builder.buildMarkGlyphSetsDef(
             [{"acute", "grave"}, {"cedilla", "grave"}], self.GLYPHMAP)