diff --git a/crates/cargo-util/src/registry.rs b/crates/cargo-util/src/registry.rs
index 6b1ccd22c..febb29bde 100644
--- a/crates/cargo-util/src/registry.rs
+++ b/crates/cargo-util/src/registry.rs
@@ -3,6 +3,12 @@
 /// - [index from of Cargo's index on filesystem][1], and
 /// - [index from Crates.io][2].
 ///
+/// <div class="warning">
+///
+/// Note: For index files, `dep_name` must have had `to_lowercase` called on it.
+///
+/// </div>
+///
 /// [1]: https://docs.rs/cargo/latest/cargo/sources/registry/index.html#the-format-of-the-index
 /// [2]: https://github.com/rust-lang/crates.io-index
 pub fn make_dep_path(dep_name: &str, prefix_only: bool) -> String {
diff --git a/src/cargo/ops/cargo_package/mod.rs b/src/cargo/ops/cargo_package/mod.rs
index 6c920eec4..5e5f4ff19 100644
--- a/src/cargo/ops/cargo_package/mod.rs
+++ b/src/cargo/ops/cargo_package/mod.rs
@@ -1068,7 +1068,8 @@ impl<'a> TmpRegistry<'a> {
             v: Some(2),
         })?;
 
-        let file = cargo_util::registry::make_dep_path(package.name().as_str(), false);
+        let file =
+            cargo_util::registry::make_dep_path(&package.name().as_str().to_lowercase(), false);
         let mut dst = self.index_path().open_rw_exclusive_create(
             file,
             self.gctx,
diff --git a/src/cargo/sources/registry/index/mod.rs b/src/cargo/sources/registry/index/mod.rs
index 87d5b0f95..bfbf67db7 100644
--- a/src/cargo/sources/registry/index/mod.rs
+++ b/src/cargo/sources/registry/index/mod.rs
@@ -584,19 +584,19 @@ impl Summaries {
     ) -> Poll<CargoResult<Option<Summaries>>> {
         // This is the file we're loading from cache or the index data.
         // See module comment in `registry/mod.rs` for why this is structured the way it is.
-        let name = &name.to_lowercase();
-        let relative = make_dep_path(&name, false);
+        let lowered_name = &name.to_lowercase();
+        let relative = make_dep_path(&lowered_name, false);
 
         let mut cached_summaries = None;
         let mut index_version = None;
-        if let Some(contents) = cache_manager.get(name) {
+        if let Some(contents) = cache_manager.get(lowered_name) {
             match Summaries::parse_cache(contents) {
                 Ok((s, v)) => {
                     cached_summaries = Some(s);
                     index_version = Some(v);
                 }
                 Err(e) => {
-                    tracing::debug!("failed to parse {name:?} cache: {e}");
+                    tracing::debug!("failed to parse {lowered_name:?} cache: {e}");
                 }
             }
         }
@@ -609,7 +609,7 @@ impl Summaries {
                 return Poll::Ready(Ok(cached_summaries));
             }
             LoadResponse::NotFound => {
-                cache_manager.invalidate(name);
+                cache_manager.invalidate(lowered_name);
                 return Poll::Ready(Ok(None));
             }
             LoadResponse::Data {
@@ -658,7 +658,7 @@ impl Summaries {
                     // Once we have our `cache_bytes` which represents the `Summaries` we're
                     // about to return, write that back out to disk so future Cargo
                     // invocations can use it.
-                    cache_manager.put(name, &cache_bytes);
+                    cache_manager.put(lowered_name, &cache_bytes);
 
                     // If we've got debug assertions enabled read back in the cached values
                     // and assert they match the expected result.
diff --git a/tests/testsuite/package.rs b/tests/testsuite/package.rs
index ae1c5d710..4d981890f 100644
--- a/tests/testsuite/package.rs
+++ b/tests/testsuite/package.rs
@@ -6430,6 +6430,68 @@ fn workspace_with_local_and_remote_deps() {
         .run();
 }
 
+#[cargo_test]
+fn workspace_with_capitalized_member() {
+    let reg = registry::init();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [workspace]
+            members = ["dep", "main"]
+            "#,
+        )
+        .file(
+            "main/Cargo.toml",
+            r#"
+            [package]
+            name = "main"
+            version = "0.0.1"
+            edition = "2015"
+            authors = []
+            license = "MIT"
+            description = "main"
+            repository = "bar"
+
+            [dependencies]
+            DEP = { path = "../dep", version = "0.1.0" }
+        "#,
+        )
+        .file("main/src/main.rs", "fn main() {}")
+        .file(
+            "dep/Cargo.toml",
+            r#"
+            [package]
+            name = "DEP"
+            version = "0.1.0"
+            edition = "2015"
+            authors = []
+            license = "MIT"
+            description = "dep"
+            repository = "bar"
+        "#,
+        )
+        .file("dep/src/lib.rs", "")
+        .build();
+
+    p.cargo("package -Zpackage-workspace --no-verify")
+        .masquerade_as_nightly_cargo(&["package-workspace"])
+        .replace_crates_io(reg.index_url())
+        .with_stderr_data(
+            str![[r#"
+[PACKAGING] main v0.0.1 ([ROOT]/foo/main)
+[UPDATING] crates.io index
+[PACKAGED] 4 files, [FILE_SIZE]B ([FILE_SIZE]B compressed)
+[PACKAGING] DEP v0.1.0 ([ROOT]/foo/dep)
+[PACKAGED] 4 files, [FILE_SIZE]B ([FILE_SIZE]B compressed)
+
+"#]]
+            .unordered(),
+        )
+        .run();
+}
+
 #[cargo_test]
 fn registry_not_in_publish_list() {
     let p = project()