diff --git a/OTFbuild/font_builder.py b/OTFbuild/font_builder.py
index 046737e..42bd6aa 100644
--- a/OTFbuild/font_builder.py
+++ b/OTFbuild/font_builder.py
@@ -213,6 +213,10 @@ def build_font(assets_dir, output_path, no_bitmap=False, no_features=False):
         g = glyphs[cp]
         if g.props.is_illegal:
             continue
+        # Skip C0/C1 control characters and DEL — some platforms render
+        # their traced bitmaps, which is undesirable.
+        if cp <= 0x001F or cp == 0x007F or 0x0080 <= cp <= 0x009F:
+            continue
         name = glyph_name(cp)
         if name == ".notdef":
             continue
diff --git a/OTFbuild/opentype_features.py b/OTFbuild/opentype_features.py
index 6877bb3..7ff025a 100644
--- a/OTFbuild/opentype_features.py
+++ b/OTFbuild/opentype_features.py
@@ -48,6 +48,26 @@ def generate_features(glyphs, kern_pairs, font_glyph_set,
     def has(cp):
         return glyph_name(cp) in font_glyph_set
 
+    preamble = """feature aalt {
+languagesystem DFLT dflt;
+languagesystem latn dflt;
+languagesystem cyrl dflt;
+languagesystem grek dflt;
+languagesystem hang KOR ;
+languagesystem hang KOH ;
+languagesystem cyrl SRB ;
+languagesystem cyrl BGR ;
+languagesystem dev2 MAR ;
+languagesystem dev2 NEP ;
+languagesystem dev2 SAN ;
+languagesystem dev2 SAT ;
+languagesystem tml2 TAM ;
+languagesystem sund SUN ;
+} aalt;
+"""
+    if preamble:
+        parts.append(preamble)
+
     # ccmp feature (replacewith directives + Hangul jamo decomposition)
     ccmp_code = _generate_ccmp(replacewith_subs or [], has)
     if ccmp_code: