diff --git a/Lib/fontTools/feaLib/ast.py b/Lib/fontTools/feaLib/ast.py
index 5289b1002..39dc4bcf8 100644
--- a/Lib/fontTools/feaLib/ast.py
+++ b/Lib/fontTools/feaLib/ast.py
@@ -821,19 +821,20 @@ class LookupFlagStatement(Statement):
                                 markAttach, markFilter)
 
     def asFea(self, indent=""):
-        res = "lookupflag"
+        res = []
         flags = ["RightToLeft", "IgnoreBaseGlyphs", "IgnoreLigatures", "IgnoreMarks"]
         curr = 1
         for i in range(len(flags)):
             if self.value & curr != 0:
-                res += " " + flags[i]
+                res.append(flags[i])
             curr = curr << 1
         if self.markAttachment is not None:
-            res += " MarkAttachmentType {}".format(self.markAttachment.asFea())
+            res.append("MarkAttachmentType {}".format(self.markAttachment.asFea()))
         if self.markFilteringSet is not None:
-            res += " UseMarkFilteringSet {}".format(self.markFilteringSet.asFea())
-        res += ";"
-        return res
+            res.append("UseMarkFilteringSet {}".format(self.markFilteringSet.asFea()))
+        if not res:
+            res = ["0"]
+        return "lookupflag {};".format(" ".join(res))
 
 
 class LookupReferenceStatement(Statement):
diff --git a/Tests/feaLib/parser_test.py b/Tests/feaLib/parser_test.py
index 764bbb006..1b51b2af0 100644
--- a/Tests/feaLib/parser_test.py
+++ b/Tests/feaLib/parser_test.py
@@ -677,6 +677,7 @@ class ParserTest(unittest.TestCase):
         self.assertEqual(flag.value, 9)
         self.assertIsNone(flag.markAttachment)
         self.assertIsNone(flag.markFilteringSet)
+        self.assertEqual(flag.asFea(), "lookupflag RightToLeft IgnoreMarks;")
 
     def test_lookupflag_format_A_MarkAttachmentType(self):
         flag = self.parse_lookupflag_(
@@ -688,6 +689,8 @@ class ParserTest(unittest.TestCase):
         self.assertEqual(flag.markAttachment.glyphSet(),
                          ("acute", "grave", "macron"))
         self.assertIsNone(flag.markFilteringSet)
+        self.assertEqual(flag.asFea(),
+            "lookupflag RightToLeft MarkAttachmentType @TOP_MARKS;")
 
     def test_lookupflag_format_A_UseMarkFilteringSet(self):
         flag = self.parse_lookupflag_(
@@ -699,6 +702,8 @@ class ParserTest(unittest.TestCase):
         self.assertIsInstance(flag.markFilteringSet, ast.GlyphClassName)
         self.assertEqual(flag.markFilteringSet.glyphSet(),
                          ("cedilla", "ogonek"))
+        self.assertEqual(flag.asFea(),
+            "lookupflag IgnoreLigatures UseMarkFilteringSet @BOTTOM_MARKS;")
 
     def test_lookupflag_format_B(self):
         flag = self.parse_lookupflag_("lookupflag 7;")
@@ -706,6 +711,16 @@ class ParserTest(unittest.TestCase):
         self.assertEqual(flag.value, 7)
         self.assertIsNone(flag.markAttachment)
         self.assertIsNone(flag.markFilteringSet)
+        self.assertEqual(flag.asFea(),
+            "lookupflag RightToLeft IgnoreBaseGlyphs IgnoreLigatures;")
+
+    def test_lookupflag_format_B_zero(self):
+        flag = self.parse_lookupflag_("lookupflag 0;")
+        self.assertIsInstance(flag, ast.LookupFlagStatement)
+        self.assertEqual(flag.value, 0)
+        self.assertIsNone(flag.markAttachment)
+        self.assertIsNone(flag.markFilteringSet)
+        self.assertEqual(flag.asFea(), "lookupflag 0;")
 
     def test_lookupflag_repeated(self):
         self.assertRaisesRegex(