diff --git a/Lib/fontTools/feaLib/ast.py b/Lib/fontTools/feaLib/ast.py
index 3b1b89321..a60ac3ec3 100644
--- a/Lib/fontTools/feaLib/ast.py
+++ b/Lib/fontTools/feaLib/ast.py
@@ -30,6 +30,11 @@ class FeatureBlock(Block):
         Block.__init__(self, location)
         self.name, self.use_extension = name, use_extension
 
+    def build(self, builder):
+        # TODO(sascha): Handle use_extension.
+        builder.start_feature(self.location, self.name)
+        Block.build(self, builder)
+
 
 class LookupBlock(Block):
     def __init__(self, location, name, use_extension):
@@ -63,6 +68,11 @@ class LanguageStatement(Statement):
         self.include_default = include_default
         self.required = required
 
+    def build(self, builder):
+        # TODO(sascha): Handle required.
+        builder.set_language(location=self.location, language=self.language,
+                             include_default=self.include_default)
+
 
 class LanguageSystemStatement(Statement):
     def __init__(self, location, script, language):
@@ -90,6 +100,9 @@ class ScriptStatement(Statement):
         Statement.__init__(self, location)
         self.script = script
 
+    def build(self, builder):
+        builder.set_script(self.location, self.script)
+
 
 class SubtableStatement(Statement):
     def __init__(self, location):
diff --git a/Lib/fontTools/feaLib/builder.py b/Lib/fontTools/feaLib/builder.py
index 1f85450e9..e3664133e 100644
--- a/Lib/fontTools/feaLib/builder.py
+++ b/Lib/fontTools/feaLib/builder.py
@@ -14,7 +14,10 @@ class Builder(object):
     def __init__(self, featurefile_path, font):
         self.featurefile_path = featurefile_path
         self.font = font
-        self.language_systems_ = []
+        self.default_language_systems_ = set()
+        self.script_ = None
+        self.lookupflag_ = 0
+        self.language_systems = set()
 
     def build(self):
         self.gpos = self.font['GPOS'] = self.makeTable('GPOS')
@@ -37,9 +40,37 @@ class Builder(object):
         return table
 
     def add_language_system(self, location, script, language):
-        if script == "DFLT" and language == "dflt" and self.language_systems_:
-            # OpenType Feature File Specification, section 4.b.i
+        # OpenType Feature File Specification, section 4.b.i
+        if (script == "DFLT" and language == "dflt" and
+                self.default_language_systems_):
             raise FeatureLibError(
                 'If "languagesystem DFLT dflt" is present, it must be '
                 'the first of the languagesystem statements', location)
-        self.language_systems_.append((script, language))
+        self.default_language_systems_.add((script, language))
+
+    def get_default_language_systems_(self):
+        # OpenType Feature File specification, 4.b.i. languagesystem:
+        # If no "languagesystem" statement is present, then the
+        # implementation must behave exactly as though the following
+        # statement were present at the beginning of the feature file:
+        # languagesystem DFLT dflt;
+        if self.default_language_systems_:
+            return frozenset(self.default_language_systems_)
+        else:
+            return frozenset({('DFLT', 'dflt')})
+
+    def start_feature(self, location, name):
+        self.language_systems = self.get_default_language_systems_()
+
+    def set_language(self, location, language, include_default):
+        if include_default:
+            langsys = set(self.get_default_language_systems_())
+        else:
+            langsys = set()
+        langsys.add((self.script_, language))
+        self.language_systems = frozenset(langsys)
+
+    def set_script(self, location, script):
+        self.script_ = script
+        self.lookupflag_ = 0
+        self.set_language(location, 'dflt', include_default=True)
diff --git a/Lib/fontTools/feaLib/builder_test.py b/Lib/fontTools/feaLib/builder_test.py
index 7eee08bb6..dfd1b0250 100644
--- a/Lib/fontTools/feaLib/builder_test.py
+++ b/Lib/fontTools/feaLib/builder_test.py
@@ -1,6 +1,6 @@
 from __future__ import print_function, division, absolute_import
 from __future__ import unicode_literals
-from fontTools.feaLib.builder import addOpenTypeFeatures
+from fontTools.feaLib.builder import Builder, addOpenTypeFeatures
 from fontTools.feaLib.error import FeatureLibError
 from fontTools.ttLib import TTFont
 import codecs
@@ -77,6 +77,19 @@ class BuilderTest(unittest.TestCase):
         addOpenTypeFeatures(self.getpath("spec4h1.fea"), font)
         self.expect_ttx(font, self.getpath("spec4h1_expected.ttx"))
 
+    def test_languagesystem(self):
+        builder = Builder(None, TTFont())
+        builder.add_language_system(None, 'latn', 'FRA')
+        builder.add_language_system(None, 'cyrl', 'RUS')
+        builder.start_feature(location=None, name='test')
+        self.assertEqual(builder.language_systems,
+                         {('latn', 'FRA'), ('cyrl', 'RUS')})
+
+    def test_languagesystem_none_specified(self):
+        builder = Builder(None, TTFont())
+        builder.start_feature(location=None, name='test')
+        self.assertEqual(builder.language_systems, {('DFLT', 'dflt')})
+
     def test_languagesystem_DFLT_dflt_not_first(self):
         self.assertRaisesRegex(
             FeatureLibError,
@@ -84,6 +97,26 @@ class BuilderTest(unittest.TestCase):
             "it must be the first of the languagesystem statements",
             self.build, "languagesystem latn TRK; languagesystem DFLT dflt;")
 
+    def test_script(self):
+        builder = Builder(None, TTFont())
+        builder.start_feature(location=None, name='test')
+        builder.set_script(location=None, script='cyrl')
+        self.assertEqual(builder.language_systems,
+                         {('DFLT', 'dflt'), ('cyrl', 'dflt')})
+
+    def test_language(self):
+        builder = Builder(None, TTFont())
+        builder.add_language_system(None, 'latn', 'FRA')
+        builder.start_feature(location=None, name='test')
+        builder.set_script(location=None, script='cyrl')
+        builder.set_language(location=None, language='RUS',
+                             include_default=False)
+        self.assertEqual(builder.language_systems, {('cyrl', 'RUS')})
+        builder.set_language(location=None, language='BGR',
+                             include_default=True)
+        self.assertEqual(builder.language_systems,
+                         {('latn', 'FRA'), ('cyrl', 'BGR')})
+
 
 if __name__ == "__main__":
     unittest.main()