diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..dfcd050
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.venv/
+.idea/
diff --git a/src/re2-stubs/__init__.pyi b/src/re2-stubs/__init__.pyi
index 2915770..c4747da 100644
--- a/src/re2-stubs/__init__.pyi
+++ b/src/re2-stubs/__init__.pyi
@@ -1,4 +1,4 @@
-from typing import AnyStr, Generic, Iterator, Literal, TypeVar, overload
+from typing import AnyStr, Generic, Iterator, Literal, TypeVar, overload, Callable
 
 # References:
 # - https://github.com/google/re2/blob/main/re2/re2.h and
@@ -99,7 +99,7 @@ def subn(
 @overload
 def sub(
     pattern: _Regexp[str] | str,
-    repl: str,
+    repl: str | Callable[[_Match[str]], str],
     text: str,
     count: int = 0,
     options: Options | None = None,
@@ -107,7 +107,7 @@ def sub(
 @overload
 def sub(
     pattern: _Regexp[bytes] | bytes,
-    repl: bytes,
+    repl: bytes | Callable[[_Match[bytes]], bytes],
     text: bytes,
     count: int = 0,
     options: Options | None = None,
@@ -185,10 +185,18 @@ class _Regexp(Generic[AnyStr]):
         self: _Regexp[bytes], repl: bytes, text: bytes, count: int = 0
     ) -> tuple[bytes, int]: ...
     @overload
-    def sub(self: _Regexp[str], repl: str, text: str, count: int = 0) -> str: ...
+    def sub(
+        self: _Regexp[str],
+        repl: str | Callable[[_Match[str]], str],
+        text: str,
+        count: int = 0,
+    ) -> str: ...
     @overload
     def sub(
-        self: _Regexp[bytes], repl: bytes, text: bytes, count: int = 0
+        self: _Regexp[bytes],
+        repl: bytes | Callable[[_Match[bytes]], bytes],
+        text: bytes,
+        count: int = 0,
     ) -> bytes: ...
     @property
     def pattern(self) -> AnyStr: ...