diff --git a/zerver/lib/ccache.py b/zerver/lib/ccache.py
index 9296a7bc67..69a63d9fe1 100644
--- a/zerver/lib/ccache.py
+++ b/zerver/lib/ccache.py
@@ -41,17 +41,17 @@ import six
 def der_encode_length(length):
     # type: (int) -> bytes
     if length <= 127:
-        return force_bytes(chr(length))
+        return struct.pack('!B', length)
     out = b""
     while length > 0:
-        out = force_bytes(chr(length & 0xff)) + out
+        out = struct.pack('!B', length & 0xff) + out
         length >>= 8
-    out = force_bytes(chr(len(out) | 0x80)) + out
+    out = struct.pack('!B', len(out) | 0x80) + out
     return out
 
 def der_encode_tlv(tag, value):
     # type: (int, bytes) -> bytes
-    return force_bytes(chr(tag)) + der_encode_length(len(value)) + value
+    return struct.pack('!B', tag) + der_encode_length(len(value)) + value
 
 def der_encode_integer_value(val):
     # type: (int) -> bytes
@@ -71,7 +71,7 @@ def der_encode_integer_value(val):
     # We can stop once sign-extension matches the remaining value.
     while val != sign:
         byte = val & 0xff
-        out = force_bytes(chr(byte)) + out
+        out = struct.pack('!B', byte) + out
         sign = -1 if byte & 0x80 == 0x80 else 0
         val >>= 8
     return out