diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 6dcb711..15d8a4b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -50,7 +50,7 @@ jobs:
           pip install ".[ci]"
       - name: "Run type checking"
         run: |
-          mypy stream_zip.py
+          mypy stream_zip.py --strict
       - name: "Run tests"
         run: |
           pytest --cov
diff --git a/stream_zip.py b/stream_zip.py
index 4acf1aa..0e83497 100644
--- a/stream_zip.py
+++ b/stream_zip.py
@@ -35,8 +35,8 @@
     object,              # Sentinel of the methods above
     object,              # Sentinel of auto upgrade central directory or not
     _CompressObjGetter,  # Function to get the zlib Compress object for
-    Optional[int],       # The uncompressed size of the file if known
-    Optional[int],       # The CRC32 of the file if known
+    int,                 # The uncompressed size of the file for NO_COMPRESSION_STREAMED_* types
+    int,                 # The CRC32 of the file for NO_COMPRESSION_STREAMED_* types
 ]
 
 # A "Method" is an instance of a class that has a _get function that returns a _MethodTuple
@@ -46,17 +46,17 @@ def _get(self, offset: int, default_get_compressobj: _CompressObjGetter) -> _Met
 
 class _ZIP_64_TYPE(Method):
     def _get(self, offset: int, default_get_compressobj: _CompressObjGetter)  -> _MethodTuple:
-        return _ZIP_64, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, None, None 
+        return _ZIP_64, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, 0, 0
 
 class _ZIP_32_TYPE(Method):
     def _get(self, offset: int, default_get_compressobj: _CompressObjGetter)  -> _MethodTuple:
-        return _ZIP_32, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, None, None
+        return _ZIP_32, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, 0, 0
 
 class _NO_COMPRESSION_32_TYPE(Method):
     def _get(self, offset: int, default_get_compressobj: _CompressObjGetter) -> _MethodTuple:
-        return _NO_COMPRESSION_BUFFERED_32, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, None, None
+        return _NO_COMPRESSION_BUFFERED_32, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, 0, 0
 
-    def __call__(self, uncompressed_size: int, crc_32: int, *args: Any, **kwarg: Any) -> Method:
+    def __call__(self, uncompressed_size: int, crc_32: int) -> Method:
         class _NO_COMPRESSION_32_TYPE_STREAMED_TYPE(Method):
             def _get(self, offset: int, default_get_compressobj: _CompressObjGetter) -> _MethodTuple:
                 return _NO_COMPRESSION_STREAMED_32, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, uncompressed_size, crc_32
@@ -65,7 +65,7 @@ def _get(self, offset: int, default_get_compressobj: _CompressObjGetter) -> _Met
 
 class _NO_COMPRESSION_64_TYPE(Method):
     def _get(self, offset: int, default_get_compressobj: _CompressObjGetter) -> _MethodTuple:
-        return _NO_COMPRESSION_BUFFERED_64, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, None, None
+        return _NO_COMPRESSION_BUFFERED_64, _NO_AUTO_UPGRADE_CENTRAL_DIRECTORY, default_get_compressobj, 0, 0
 
     def __call__(self, uncompressed_size: int, crc_32: int) -> Method:
         class _NO_COMPRESSION_64_TYPE_STREAMED_TYPE(Method):
@@ -91,7 +91,7 @@ def __call__(self, uncompressed_size: int, level: int=9) -> Method:
         class _ZIP_AUTO_TYPE_INNER(Method):
             def _get(self, offset: int, default_get_compressobj: _CompressObjGetter) -> _MethodTuple:
                 method = _ZIP_64 if uncompressed_size > 4293656841 or offset > 0xffffffff else _ZIP_32
-                return (method, _AUTO_UPGRADE_CENTRAL_DIRECTORY, lambda: zlib.compressobj(level=level, memLevel=8, wbits=-zlib.MAX_WBITS), None, None)
+                return (method, _AUTO_UPGRADE_CENTRAL_DIRECTORY, lambda: zlib.compressobj(level=level, memLevel=8, wbits=-zlib.MAX_WBITS), 0, 0)
 
         return _ZIP_AUTO_TYPE_INNER()
 
@@ -246,7 +246,12 @@ def _encrypt_aes(chunks: Generator[bytes, None, Any]) -> Generator[bytes, None,
                 return get_return_value()
             return _encrypt_aes
 
-        def _zip_64_local_header_and_data(compression, aes_size_increase, aes_flags, name_encoded, mod_at_ms_dos, mod_at_unix_extra, aes_extra, external_attr, uncompressed_size, crc_32, crc_32_mask, _get_compress_obj, encryption_func, chunks) -> Generator[bytes, None, Any]:
+        def _zip_64_local_header_and_data(
+                compression: int, aes_size_increase: int, aes_flags: int, name_encoded: bytes, mod_at_ms_dos: bytes,
+                mod_at_unix_extra: bytes, aes_extra: bytes, external_attr: int, uncompressed_size: int, crc_32: int,
+                crc_32_mask: int, _get_compress_obj: _CompressObjGetter, encryption_func: Callable[[Generator[bytes, None, Any]], Generator[bytes, None, Any]],
+                chunks: Iterable[bytes],
+        ) -> Generator[bytes, None, Tuple[bytes, bytes, bytes]]:
             file_offset = offset
 
             _raise_if_beyond(file_offset, maximum=0xffffffffffffffff, exception_class=OffsetOverflowError)
@@ -313,7 +318,12 @@ def _zip_64_local_header_and_data(compression, aes_size_increase, aes_flags, nam
                 0xffffffff,   # Offset of local header - since zip64
             ), name_encoded, extra
 
-        def _zip_32_local_header_and_data(compression, aes_size_increase, aes_flags, name_encoded, mod_at_ms_dos, mod_at_unix_extra, aes_extra, external_attr, uncompressed_size, crc_32, crc_32_mask, _get_compress_obj, encryption_func, chunks) -> Generator[bytes, None, Any]:
+        def _zip_32_local_header_and_data(
+                compression: int, aes_size_increase: int, aes_flags: int, name_encoded: bytes, mod_at_ms_dos: bytes,
+                mod_at_unix_extra: bytes, aes_extra: bytes, external_attr: int, uncompressed_size: int, crc_32: int,
+                crc_32_mask: int, _get_compress_obj: _CompressObjGetter, encryption_func: Callable[[Generator[bytes, None, Any]], Generator[bytes, None, Any]],
+                chunks: Iterable[bytes],
+        ) -> Generator[bytes, None, Tuple[bytes, bytes, bytes]]:
             file_offset = offset
 
             _raise_if_beyond(file_offset, maximum=0xffffffff, exception_class=OffsetOverflowError)
@@ -368,7 +378,8 @@ def _zip_32_local_header_and_data(compression, aes_size_increase, aes_flags, nam
                 file_offset,
             ), name_encoded, extra
 
-        def _zip_data(chunks, _get_compress_obj, max_uncompressed_size, max_compressed_size) -> Generator[bytes, None, Any]:
+        def _zip_data(chunks: Iterable[bytes], _get_compress_obj: _CompressObjGetter,
+                      max_uncompressed_size: int, max_compressed_size: int) -> Generator[bytes, None, Tuple[int, int, int]]:
             uncompressed_size = 0
             compressed_size = 0
             crc_32 = zlib.crc32(b'')
@@ -395,7 +406,12 @@ def _zip_data(chunks, _get_compress_obj, max_uncompressed_size, max_compressed_s
 
             return uncompressed_size, compressed_size, crc_32
 
-        def _no_compression_64_local_header_and_data(compression, aes_size_increase, aes_flags, name_encoded, mod_at_ms_dos, mod_at_unix_extra, aes_extra, external_attr, uncompressed_size, crc_32, crc_32_mask, _get_compress_obj, encryption_func, chunks) -> Generator[bytes, None, Any]:
+        def _no_compression_64_local_header_and_data(
+                compression: int, aes_size_increase: int, aes_flags: int, name_encoded: bytes, mod_at_ms_dos: bytes,
+                mod_at_unix_extra: bytes, aes_extra: bytes, external_attr: int, uncompressed_size: int, crc_32: int,
+                crc_32_mask: int, _get_compress_obj: _CompressObjGetter, encryption_func: Callable[[Generator[bytes, None, Any]], Generator[bytes, None, Any]],
+                chunks: Iterable[bytes],
+        ) -> Generator[bytes, None, Tuple[bytes, bytes, bytes]]:
             file_offset = offset
 
             _raise_if_beyond(file_offset, maximum=0xffffffffffffffff, exception_class=OffsetOverflowError)
@@ -427,7 +443,7 @@ def _no_compression_64_local_header_and_data(compression, aes_size_increase, aes
             yield from _(name_encoded)
             yield from _(extra)
 
-            yield from encryption_func(chunks)
+            yield from encryption_func((chunk for chunk in chunks))
 
             extra = zip_64_central_directory_extra_struct.pack(
                 zip_64_extra_signature,
@@ -457,7 +473,12 @@ def _no_compression_64_local_header_and_data(compression, aes_size_increase, aes
             ), name_encoded, extra
 
 
-        def _no_compression_32_local_header_and_data(compression, aes_size_increase, aes_flags, name_encoded, mod_at_ms_dos, mod_at_unix_extra, aes_extra, external_attr, uncompressed_size, crc_32, crc_32_mask, _get_compress_obj, encryption_func, chunks) -> Generator[bytes, None, Any]:
+        def _no_compression_32_local_header_and_data(
+                compression: int, aes_size_increase: int, aes_flags: int, name_encoded: bytes, mod_at_ms_dos: bytes,
+                mod_at_unix_extra: bytes, aes_extra: bytes, external_attr: int, uncompressed_size: int, crc_32: int,
+                crc_32_mask: int, _get_compress_obj: _CompressObjGetter, encryption_func: Callable[[Generator[bytes, None, Any]], Generator[bytes, None, Any]],
+                chunks: Iterable[bytes],
+        ) -> Generator[bytes, None, Tuple[bytes, bytes, bytes]]:
             file_offset = offset
 
             _raise_if_beyond(file_offset, maximum=0xffffffff, exception_class=OffsetOverflowError)
@@ -484,7 +505,7 @@ def _no_compression_32_local_header_and_data(compression, aes_size_increase, aes
             yield from _(name_encoded)
             yield from _(extra)
 
-            yield from encryption_func(chunks)
+            yield from encryption_func((chunk for chunk in chunks))
 
             return central_directory_header_struct.pack(
                20,           # Version made by
@@ -513,7 +534,7 @@ def _no_compression_buffered_data_size_crc_32(chunks: Iterable[bytes], maximum_s
             size = 0
             crc_32 = zlib.crc32(b'')
 
-            def _chunks() -> Iterable[bytes]:
+            def _chunks() -> Generator[bytes, None, Any]:
                 nonlocal size, crc_32
                 for chunk in chunks:
                     size += len(chunk)
@@ -521,11 +542,16 @@ def _chunks() -> Iterable[bytes]:
                     crc_32 = zlib.crc32(chunk, crc_32)
                     yield chunk
 
-            chunks = tuple(_chunks())
+            __chunks = tuple(_chunks())
 
-            return chunks, size, crc_32
+            return __chunks, size, crc_32
 
-        def _no_compression_streamed_64_local_header_and_data(compression, aes_size_increase, aes_flags, name_encoded, mod_at_ms_dos, mod_at_unix_extra, aes_extra, external_attr, uncompressed_size, crc_32, crc_32_mask, _get_compress_obj, encryption_func, chunks) -> Generator[bytes, None, Any]:
+        def _no_compression_streamed_64_local_header_and_data(
+                compression: int, aes_size_increase: int, aes_flags: int, name_encoded: bytes, mod_at_ms_dos: bytes,
+                mod_at_unix_extra: bytes, aes_extra: bytes, external_attr: int, uncompressed_size: int, crc_32: int,
+                crc_32_mask: int, _get_compress_obj: _CompressObjGetter, encryption_func: Callable[[Generator[bytes, None, Any]], Generator[bytes, None, Any]],
+                chunks: Iterable[bytes],
+        ) -> Generator[bytes, None, Tuple[bytes, bytes, bytes]]:
             file_offset = offset
 
             _raise_if_beyond(file_offset, maximum=0xffffffffffffffff, exception_class=OffsetOverflowError)
@@ -585,7 +611,12 @@ def _no_compression_streamed_64_local_header_and_data(compression, aes_size_incr
             ), name_encoded, extra
 
 
-        def _no_compression_streamed_32_local_header_and_data(compression, aes_size_increase, aes_flags, name_encoded, mod_at_ms_dos, mod_at_unix_extra, aes_extra, external_attr, uncompressed_size, crc_32, crc_32_mask, _get_compress_obj, encryption_func, chunks) -> Generator[bytes, None, Any]:
+        def _no_compression_streamed_32_local_header_and_data(
+                compression: int, aes_size_increase: int, aes_flags: int, name_encoded: bytes, mod_at_ms_dos: bytes,
+                mod_at_unix_extra: bytes, aes_extra: bytes, external_attr: int, uncompressed_size: int, crc_32: int,
+                crc_32_mask: int, _get_compress_obj: _CompressObjGetter, encryption_func: Callable[[Generator[bytes, None, Any]], Generator[bytes, None, Any]],
+                chunks: Iterable[bytes],
+        ) -> Generator[bytes, None, Any]:
             file_offset = offset
 
             _raise_if_beyond(file_offset, maximum=0xffffffff, exception_class=OffsetOverflowError)
@@ -632,7 +663,7 @@ def _no_compression_streamed_32_local_header_and_data(compression, aes_size_incr
                file_offset,
             ), name_encoded, extra
 
-        def _no_compression_streamed_data(chunks, uncompressed_size, crc_32, maximum_size) -> Generator[bytes, None, Any]:
+        def _no_compression_streamed_data(chunks: Iterable[bytes], uncompressed_size: int, crc_32: int, maximum_size: int) -> Generator[bytes, None, Any]:
             actual_crc_32 = zlib.crc32(b'')
             size = 0
             for chunk in chunks: