diff --git a/CHANGELOG.md b/CHANGELOG.md
index b0518c1..021f2d7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ All notable changes to htmltools for Python will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [UNRELEASED]
+
+* The `HTMLDependency.copy()` method can now correctly copy folders in depenendencies that both include directories and have `all_files=True`. (#87)
+
 ## [0.5.1] 2023-12-18
 
 * `Tag` objects can now be used as context managers, as in `with tags.div():`. When used this way, then inside the `with` block, `sys.displayhook` is replaced with a function which adds items as children to the `Tag`. This is meant to be used with Shiny Express, Quarto, or Jupyter. (#76)
diff --git a/htmltools/_core.py b/htmltools/_core.py
index 8c71287..d2feb9d 100644
--- a/htmltools/_core.py
+++ b/htmltools/_core.py
@@ -133,8 +133,7 @@ class Tagifiable(Protocol):
     returns a `TagList`, the children of the `TagList` must also be tagified.
     """
 
-    def tagify(self) -> "TagList | Tag | MetadataNode | str":
-        ...
+    def tagify(self) -> "TagList | Tag | MetadataNode | str": ...
 
 
 @runtime_checkable
@@ -148,8 +147,7 @@ def __call__(
         *args: TagChild | TagAttrs,
         _add_ws: TagAttrValue = ...,
         **kwargs: TagAttrValue,
-    ) -> "Tag":
-        ...
+    ) -> "Tag": ...
 
 
 @runtime_checkable
@@ -158,8 +156,7 @@ class ReprHtml(Protocol):
     Objects with a `_repr_html_()` method.
     """
 
-    def _repr_html_(self) -> str:
-        ...
+    def _repr_html_(self) -> str: ...
 
 
 # =============================================================================
@@ -1609,7 +1606,7 @@ def copy_to(self, path: str, include_version: bool = True) -> None:
         # Verify they all exist
         for f in src_files:
             src_file = os.path.join(paths["source"], f)
-            if not os.path.isfile(src_file):
+            if not os.path.exists(src_file):
                 raise Exception(
                     f"Failed to copy HTML dependency {self.name}-{str(self.version)} "
                     + f"because {src_file} doesn't exist."
@@ -1626,7 +1623,10 @@ def copy_to(self, path: str, include_version: bool = True) -> None:
             src_file = os.path.join(paths["source"], f)
             target_file = os.path.join(target_dir, f)
             os.makedirs(os.path.dirname(target_file), exist_ok=True)
-            shutil.copy2(src_file, target_file)
+            if os.path.isfile(src_file):
+                shutil.copy2(src_file, target_file)
+            elif os.path.isdir(src_file):
+                shutil.copytree(src_file, target_file)
 
     def _validate_dicts(self, ld: Iterable[object], req_attr: list[str]) -> None:
         for d in ld:
@@ -1740,7 +1740,7 @@ def _tag_show(
             import IPython  # pyright: ignore[reportUnknownVariableType]
 
             ipy = (  # pyright: ignore[reportUnknownVariableType]
-                IPython.get_ipython()  # pyright: ignore[reportUnknownMemberType]
+                IPython.get_ipython()  # pyright: ignore[reportUnknownMemberType, reportPrivateImportUsage]
             )
             renderer = "ipython" if ipy else "browser"
         except ImportError:
diff --git a/htmltools/_jsx.py b/htmltools/_jsx.py
index 6d75ddb..02a1c9d 100644
--- a/htmltools/_jsx.py
+++ b/htmltools/_jsx.py
@@ -4,6 +4,7 @@
 that's an issue for HTML() and <script> tags, so using normal HTML tags inside JSX
 components may become unsupported in a future version (see #26 and #28)
 """
+
 from __future__ import annotations
 
 import copy
diff --git a/pyproject.toml b/pyproject.toml
index 03047a0..4328d46 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -65,7 +65,7 @@ version = {attr = "htmltools.__version__"}
 htmltools = ["py.typed"]
 
 [tool.flake8]
-ignore = "E203, E302, E402, E501, F403, F405, W503"
+ignore = "E203, E302, E402, E501, E704, F403, F405, W503"
 extend-exclude = "docs, .venv, venv, typings, e2e, build"
 
 [tool.isort]
diff --git a/tests/assets/css/my-styles.css b/tests/assets/testdep-nested/css/my-styles.css
similarity index 100%
rename from tests/assets/css/my-styles.css
rename to tests/assets/testdep-nested/css/my-styles.css
diff --git a/tests/assets/js/my-js.js b/tests/assets/testdep-nested/js/my-js.js
similarity index 100%
rename from tests/assets/js/my-js.js
rename to tests/assets/testdep-nested/js/my-js.js
diff --git a/tests/test_deps.py b/tests/test_deps.py
index f436b6a..b166bdf 100644
--- a/tests/test_deps.py
+++ b/tests/test_deps.py
@@ -354,3 +354,15 @@ def test_copy_to():
         dep4.copy_to(tmpdir4)
         assert (Path(tmpdir4) / "w-1.0" / "testdep.css").exists()
         assert (Path(tmpdir4) / "w-1.0" / "testdep.js").exists()
+
+    with tempfile.TemporaryDirectory() as tmpdir5:
+        path_testdep_nested = Path(__file__).parent / "assets" / "testdep-nested"
+        dep5 = HTMLDependency(
+            "w",
+            "1.0",
+            source={"subdir": str(path_testdep_nested)},
+            all_files=True,
+        )
+        dep5.copy_to(tmpdir5)
+        assert (Path(tmpdir5) / "w-1.0" / "css" / "my-styles.css").exists()
+        assert (Path(tmpdir5) / "w-1.0" / "js" / "my-js.js").exists()
diff --git a/tests/test_tags.py b/tests/test_tags.py
index 6e3e22b..29476bd 100644
--- a/tests/test_tags.py
+++ b/tests/test_tags.py
@@ -99,7 +99,7 @@ def test_basic_tag_api():
     assert "style" not in x4.attrs.keys()
     try:
         x4.add_style("color: red")
-        assert False, "Expected ValueError for missing semicolon"
+        raise AssertionError("Expected ValueError for missing semicolon")
     except ValueError as e:
         assert "must end with a semicolon" in str(e)