diff --git a/git-discover/src/repository.rs b/git-discover/src/repository.rs
index 25c0730d304..0d6cf060bb1 100644
--- a/git-discover/src/repository.rs
+++ b/git-discover/src/repository.rs
@@ -116,7 +116,7 @@ pub enum Kind {
     ///
     /// Note that this is merely a guess at this point as we didn't read the configuration yet.
     Bare,
-    /// A `git` repository along with a checked out files in a work tree.
+    /// A `git` repository along with checked out files in a work tree.
     WorkTree {
         /// If set, this is the git dir associated with this _linked_ worktree.
         /// If `None`, the git_dir is the `.git` directory inside the _main_ worktree we represent.
diff --git a/git-repository/src/config/cache/incubate.rs b/git-repository/src/config/cache/incubate.rs
index 233b4c0f3e6..7861b643f2d 100644
--- a/git-repository/src/config/cache/incubate.rs
+++ b/git-repository/src/config/cache/incubate.rs
@@ -15,27 +15,20 @@ pub(crate) struct StageOne {
 /// Initialization
 impl StageOne {
     pub fn new(
+        common_dir: &std::path::Path,
         git_dir: &std::path::Path,
         git_dir_trust: git_sec::Trust,
         lossy: Option<bool>,
         lenient: bool,
     ) -> Result<Self, Error> {
         let mut buf = Vec::with_capacity(512);
-        let config = {
-            let config_path = git_dir.join("config");
-            std::io::copy(&mut std::fs::File::open(&config_path)?, &mut buf)?;
-
-            git_config::File::from_bytes_owned(
-                &mut buf,
-                git_config::file::Metadata::from(git_config::Source::Local)
-                    .at(config_path)
-                    .with(git_dir_trust),
-                git_config::file::init::Options {
-                    includes: git_config::file::includes::Options::no_follow(),
-                    ..util::base_options(lossy)
-                },
-            )?
-        };
+        let mut config = load_config(
+            common_dir.join("config"),
+            &mut buf,
+            git_config::Source::Local,
+            git_dir_trust,
+            lossy,
+        )?;
 
         let is_bare = util::config_bool(&config, "core.bare", false, lenient)?;
         let repo_format_version = config
@@ -57,6 +50,18 @@ impl StageOne {
             .transpose()?
             .unwrap_or(git_hash::Kind::Sha1);
 
+        let extension_worktree = util::config_bool(&config, "extensions.worktreeConfig", false, lenient)?;
+        if extension_worktree {
+            let worktree_config = load_config(
+                git_dir.join("config.worktree"),
+                &mut buf,
+                git_config::Source::Worktree,
+                git_dir_trust,
+                lossy,
+            )?;
+            config.append(worktree_config);
+        };
+
         let reflog = util::query_refupdates(&config, lenient)?;
         Ok(StageOne {
             git_dir_config: config,
@@ -68,3 +73,27 @@ impl StageOne {
         })
     }
 }
+
+fn load_config(
+    config_path: std::path::PathBuf,
+    buf: &mut Vec<u8>,
+    source: git_config::Source,
+    git_dir_trust: git_sec::Trust,
+    lossy: Option<bool>,
+) -> Result<git_config::File<'static>, Error> {
+    buf.clear();
+    std::io::copy(&mut std::fs::File::open(&config_path)?, buf)?;
+
+    let config = git_config::File::from_bytes_owned(
+        buf,
+        git_config::file::Metadata::from(source)
+            .at(config_path)
+            .with(git_dir_trust),
+        git_config::file::init::Options {
+            includes: git_config::file::includes::Options::no_follow(),
+            ..util::base_options(lossy)
+        },
+    )?;
+
+    Ok(config)
+}
diff --git a/git-repository/src/open/repository.rs b/git-repository/src/open/repository.rs
index b3a14f92571..5953a54f440 100644
--- a/git-repository/src/open/repository.rs
+++ b/git-repository/src/open/repository.rs
@@ -133,7 +133,13 @@ impl ThreadSafeRepository {
             .map(|cd| git_dir.join(cd));
         let common_dir_ref = common_dir.as_deref().unwrap_or(&git_dir);
 
-        let repo_config = config::cache::StageOne::new(common_dir_ref, git_dir_trust, lossy_config, lenient_config)?;
+        let repo_config = config::cache::StageOne::new(
+            common_dir_ref,
+            git_dir.as_ref(),
+            git_dir_trust,
+            lossy_config,
+            lenient_config,
+        )?;
         let mut refs = {
             let reflog = repo_config.reflog.unwrap_or(git_ref::store::WriteReflog::Disable);
             let object_hash = repo_config.object_hash;
diff --git a/git-repository/src/repository/permissions.rs b/git-repository/src/repository/permissions.rs
index aab98c6799b..b1d51364c46 100644
--- a/git-repository/src/repository/permissions.rs
+++ b/git-repository/src/repository/permissions.rs
@@ -9,7 +9,9 @@ pub struct Permissions {
     pub config: Config,
 }
 
-/// Configure security relevant options when loading a git configuration.
+/// Configure from which sources git configuration may be loaded.
+///
+/// Note that configuration from inside of the repository is always loaded as it's definitely required for correctness.
 #[derive(Copy, Clone, Ord, PartialOrd, PartialEq, Eq, Debug, Hash)]
 pub struct Config {
     /// The git binary may come with configuration as part of its configuration, and if this is true (default false)
@@ -29,9 +31,6 @@ pub struct Config {
     /// Whether to use the user configuration.
     /// This is usually `~/.gitconfig` on unix.
     pub user: bool,
-    // TODO: figure out how this really applies and provide more information here.
-    // Whether to use worktree configuration from `config.worktree`.
-    // pub worktree: bool,
     /// Whether to use the configuration from environment variables.
     pub env: bool,
     /// Whether to follow include files are encountered in loaded configuration,
diff --git a/git-repository/tests/fixtures/generated-archives/.gitignore b/git-repository/tests/fixtures/generated-archives/.gitignore
index 9f4f7db5774..8895a24ab87 100644
--- a/git-repository/tests/fixtures/generated-archives/.gitignore
+++ b/git-repository/tests/fixtures/generated-archives/.gitignore
@@ -1,4 +1,5 @@
 /make_worktree_repo.tar.xz
+/make_worktree_repo_with_configs.tar.xz
 /make_remote_repos.tar.xz
 /make_fetch_repos.tar.xz
 /make_core_worktree_repo.tar.xz
diff --git a/git-repository/tests/fixtures/make_worktree_repo_with_configs.sh b/git-repository/tests/fixtures/make_worktree_repo_with_configs.sh
new file mode 100644
index 00000000000..f1c046d7987
--- /dev/null
+++ b/git-repository/tests/fixtures/make_worktree_repo_with_configs.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+
+set -eu -o pipefail
+
+git init repo
+
+(cd repo
+  touch a b c
+  git add .
+  git commit -m initial
+
+  git worktree add ../wt-1
+  git worktree add ../wt-2
+
+  git config extensions.worktreeConfig true
+  git config --worktree worktree.setting "set in the main worktree"
+
+  git config shared.setting "set in the shared config"
+  git config override.setting "set in the shared config"
+)
+
+(cd wt-1
+  git config --worktree worktree.setting "set in wt-1"
+)
+
+(cd wt-2
+  git config --worktree worktree.setting "set in wt-2"
+  git config --worktree override.setting "override in wt-2"
+)
diff --git a/git-repository/tests/repository/open.rs b/git-repository/tests/repository/open.rs
index a0fdc013027..3768f74c5e3 100644
--- a/git-repository/tests/repository/open.rs
+++ b/git-repository/tests/repository/open.rs
@@ -225,3 +225,104 @@ mod with_overrides {
         Cow::Borrowed(s.into())
     }
 }
+
+mod worktree {
+    use git_repository::open;
+
+    #[test]
+    fn with_worktree_configs() -> git_testtools::Result {
+        let manifest_dir = std::path::PathBuf::from(std::env::var("CARGO_MANIFEST_DIR")?);
+        let fixture_dir = git_testtools::scripted_fixture_repo_read_only("make_worktree_repo_with_configs.sh")?;
+        let worktree_base = manifest_dir.join(&fixture_dir).join("repo/.git/worktrees");
+
+        {
+            let base = open(fixture_dir.join("repo"))?;
+            let base_config = base.config_snapshot();
+
+            assert_eq!(
+                base.work_dir(),
+                Some(fixture_dir.join("repo").as_path()),
+                "the main worktree"
+            );
+            assert_eq!(base.git_dir(), fixture_dir.join("repo/.git"), "git dir and…");
+            assert_eq!(
+                base.common_dir(),
+                fixture_dir.join("repo/.git"),
+                "…common dir are the same"
+            );
+
+            assert_eq!(
+                base_config.string("worktree.setting").expect("exists").as_ref(),
+                "set in the main worktree"
+            );
+            assert_eq!(
+                base_config.string("shared.setting").expect("exists").as_ref(),
+                "set in the shared config"
+            );
+            assert_eq!(
+                base_config.string("override.setting").expect("exists").as_ref(),
+                "set in the shared config"
+            );
+        }
+
+        {
+            let wt1 = open(fixture_dir.join("wt-1"))?;
+            let wt1_config = wt1.config_snapshot();
+            assert_eq!(
+                wt1.work_dir(),
+                Some(fixture_dir.join("wt-1").as_path()),
+                "a linked worktree in its own location"
+            );
+            assert_eq!(
+                wt1.git_dir(),
+                worktree_base.join("wt-1"),
+                "whose git-dir is within the common dir"
+            );
+            assert_eq!(
+                wt1.common_dir(),
+                worktree_base.join("wt-1/../.."),
+                "the common dir is the `git-dir` of the repository with the main worktree"
+            );
+
+            assert_eq!(
+                wt1_config.string("worktree.setting").expect("exists").as_ref(),
+                "set in wt-1"
+            );
+            assert_eq!(
+                wt1_config.string("shared.setting").expect("exists").as_ref(),
+                "set in the shared config"
+            );
+            assert_eq!(
+                wt1_config.string("override.setting").expect("exists").as_ref(),
+                "set in the shared config"
+            );
+        }
+
+        {
+            let wt2 = open(fixture_dir.join("wt-2"))?;
+            let wt2_config = wt2.config_snapshot();
+            assert_eq!(
+                wt2.work_dir(),
+                Some(fixture_dir.join("wt-2").as_path()),
+                "another linked worktree as sibling to wt-1"
+            );
+            assert_eq!(wt2.git_dir(), worktree_base.join("wt-2"));
+            assert_eq!(wt2.common_dir(), worktree_base.join("wt-2/../.."));
+
+            assert_eq!(
+                wt2_config.string("worktree.setting").expect("exists").as_ref(),
+                "set in wt-2"
+            );
+            assert_eq!(
+                wt2_config.string("shared.setting").expect("exists").as_ref(),
+                "set in the shared config"
+            );
+            assert_eq!(
+                wt2_config.string("override.setting").expect("exists").as_ref(),
+                "override in wt-2"
+            );
+        }
+
+        Ok(())
+    }
+}