diff --git a/tests/utils_test.py b/tests/utils_test.py
index a1c506b..7fe138e 100644
--- a/tests/utils_test.py
+++ b/tests/utils_test.py
@@ -16,8 +16,9 @@ class TestUtils(unittest.TestCase):
 
     def test_binary_parameters(self):
         cases = {
-            39: (5, 64, 14),
-            10: (3, 16, 4)
+            39: (32, 5),
+            10: (8, 3),
+            19: (16, 4)
         }
         for n, result in cases.items():
             self.assertEqual(binary_search_parameters(n), result)
diff --git a/zttf/subset.py b/zttf/subset.py
index 0103c73..3e9bbe7 100644
--- a/zttf/subset.py
+++ b/zttf/subset.py
@@ -118,7 +118,7 @@ class TTFSubset:
         self.cmap_ranges[-1].iddelta = 0
 
         seg_count = len(self.cmap_ranges)
-        src_range, entry_selector, range_shift = binary_search_parameters(seg_count * 2)
+        src_range, entry_selector = binary_search_parameters(seg_count * 2)
         length = 16 + 8 * seg_count + len(self.glyph_to_char) + 1
 
         data = [
@@ -195,7 +195,8 @@ class TTFSubset:
         st.coverage = 1
         kern.write(st.as_bytes())
         kern.write(pack(">H", len(entries)))
-        kern.write(pack(">HHH", *binary_search_parameters(len(entries))))
+        src_rng, sel = binary_search_parameters(len(entries))
+        kern.write(pack(">HHH", src_rng, sel, len(entries) - sel * calcsize(">HHH")))
         for key, diff in entries.items():
             kern.write(pack(">HHh", key[0], key[1], diff))
 
@@ -220,7 +221,9 @@ class TTFSubset:
         header.version_raw = 0x00010000
 
         output = BytesIO()
-        header.entry_selector, header.search_range, header.range_shift = binary_search_parameters(len(self.tables))
+        header.search_range, header.entry_selector = binary_search_parameters(len(self.tables))
+        header.search_range *= 16
+        header.range_shift = len(self.tables) * 16 - header.search_range
         output.write(header.as_bytes())
 
         head_offset = 0
diff --git a/zttf/utils.py b/zttf/utils.py
index b878a13..f137a27 100644
--- a/zttf/utils.py
+++ b/zttf/utils.py
@@ -98,15 +98,14 @@ def binary_search_parameters(length):
     """ The TTF specification has several places that require binary search
         parameters. For an example look at the CMAP Format 4 table.
     :param length: The range over which the search will be performed.
-    :return: The 3 parameters required.
+    :return: The 2 parameters required.
     """
     search_range = 2
     entry_selector = 1
     while search_range * 2 <= length:
         search_range *= 2
         entry_selector += 1
-    search_range *= 2
-    return entry_selector, search_range, 2 * length - search_range
+    return search_range, entry_selector
 
 
 class Range: