diff --git a/src/dbus_fast/_private/marshaller.pxd b/src/dbus_fast/_private/marshaller.pxd
index 7ac3aaf..6995d68 100644
--- a/src/dbus_fast/_private/marshaller.pxd
+++ b/src/dbus_fast/_private/marshaller.pxd
@@ -3,9 +3,12 @@
 import cython
 
 
-cdef bytes PACKED_UINT32_ZERO
 cdef object PACK_UINT32
 
+cdef bytes PACKED_UINT32_ZERO
+cdef bytes PACKED_BOOL_TRUE
+cdef bytes PACKED_BOOL_FALSE
+
 cdef class Marshaller:
 
     cdef object signature_tree
diff --git a/src/dbus_fast/_private/marshaller.py b/src/dbus_fast/_private/marshaller.py
index 3118900..ecfa259 100644
--- a/src/dbus_fast/_private/marshaller.py
+++ b/src/dbus_fast/_private/marshaller.py
@@ -5,6 +5,8 @@ from ..signature import SignatureType, Variant, get_signature_tree
 
 PACK_UINT32 = Struct("<I").pack
 PACKED_UINT32_ZERO = PACK_UINT32(0)
+PACKED_BOOL_FALSE = PACK_UINT32(int(0))
+PACKED_BOOL_TRUE = PACK_UINT32(int(1))
 
 
 class Marshaller:
@@ -34,7 +36,7 @@ class Marshaller:
 
     def write_boolean(self, boolean: bool, type_: SignatureType) -> int:
         written = self._align(4)
-        self._buf.extend(PACK_UINT32(int(boolean)))
+        self._buf += PACKED_BOOL_TRUE if boolean else PACKED_BOOL_FALSE
         return written + 4
 
     def write_signature(self, signature: str, type_: SignatureType) -> int: