diff --git a/crates/fmm-core/src/manifest/dependency_matcher/path.rs b/crates/fmm-core/src/manifest/dependency_matcher/path.rs
index e485bd4..1a2f1c4 100644
--- a/crates/fmm-core/src/manifest/dependency_matcher/path.rs
+++ b/crates/fmm-core/src/manifest/dependency_matcher/path.rs
@@ -3,7 +3,7 @@ use std::path::Path;
 use std::sync::OnceLock;
 
 use crate::manifest::Manifest;
-use crate::resolver::workspace::WorkspaceEcosystem;
+use crate::resolver::{relative_importer_starts_with_package_dir, workspace::WorkspaceEcosystem};
 
 const JS_TS_SOURCE_EXTENSIONS: &[&str] = &["ts", "tsx", "js", "jsx", "mjs", "cjs"];
 const RUST_SOURCE_EXTENSIONS: &[&str] = &["rs"];
@@ -32,7 +32,10 @@ pub(super) fn is_cargo_workspace_source(path: &Path, manifest: &Manifest) -> boo
         && manifest
             .workspace_packages_for(WorkspaceEcosystem::Rust)
             .values()
-            .any(|dir| path.starts_with(dir) && dir.join("Cargo.toml").exists())
+            .any(|dir| {
+                (path.starts_with(dir) || relative_importer_starts_with_package_dir(path, dir))
+                    && dir.join("Cargo.toml").exists()
+            })
 }
 
 /// Return a reference to the lazily initialised set of source file extensions
diff --git a/crates/fmm-core/src/manifest/dependency_matcher_review_tests.rs b/crates/fmm-core/src/manifest/dependency_matcher_review_tests.rs
index 0ebc47a..aeac72e 100644
--- a/crates/fmm-core/src/manifest/dependency_matcher_review_tests.rs
+++ b/crates/fmm-core/src/manifest/dependency_matcher_review_tests.rs
@@ -206,3 +206,89 @@ rtm-core = { path = "../rtm-core" }
     );
     assert!(lib_importers.contains(&cli_main_key), "{lib_importers:?}");
 }
+
+#[test]
+fn rust_crate_import_with_relative_manifest_keys_stays_in_importer_crate() {
+    let tmp = tempfile::TempDir::new().unwrap();
+    write_file(
+        tmp.path(),
+        "crates/fmm-core/Cargo.toml",
+        r#"
+[package]
+name = "fmm-core"
+version = "0.1.0"
+edition = "2024"
+"#,
+    );
+    write_file(
+        tmp.path(),
+        "crates/fmm-cli/Cargo.toml",
+        r#"
+[package]
+name = "fmm-cli"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+fmm-core = { path = "../fmm-core" }
+"#,
+    );
+    write_file(tmp.path(), "crates/fmm-core/src/lib.rs", "pub mod dupes;");
+    write_file(
+        tmp.path(),
+        "crates/fmm-core/src/dupes.rs",
+        "pub struct DupeClustersResult;",
+    );
+    write_file(
+        tmp.path(),
+        "crates/fmm-core/src/format/search_formatters.rs",
+        "use crate::dupes::DupeClustersResult;",
+    );
+    write_file(
+        tmp.path(),
+        "crates/fmm-cli/src/cli/commands/dupes.rs",
+        "pub fn dupes() {}",
+    );
+
+    let core_dupes_key = "crates/fmm-core/src/dupes.rs".to_string();
+    let search_formatters_key = "crates/fmm-core/src/format/search_formatters.rs".to_string();
+    let cli_dupes_key = "crates/fmm-cli/src/cli/commands/dupes.rs".to_string();
+    let mut manifest = Manifest::new();
+    manifest.workspace_packages = HashMap::from([
+        ("fmm_core".to_string(), tmp.path().join("crates/fmm-core")),
+        ("fmm_cli".to_string(), tmp.path().join("crates/fmm-cli")),
+    ]);
+    manifest.files.insert(
+        core_dupes_key.clone(),
+        crate::manifest::FileEntry::default(),
+    );
+    manifest.files.insert(
+        search_formatters_key.clone(),
+        crate::manifest::FileEntry {
+            dependencies: vec!["crate::dupes".to_string()],
+            ..Default::default()
+        },
+    );
+    manifest
+        .files
+        .insert(cli_dupes_key.clone(), crate::manifest::FileEntry::default());
+
+    let reverse_deps = build_reverse_deps(&manifest);
+    let core_dupes_importers = reverse_deps
+        .get(&core_dupes_key)
+        .cloned()
+        .unwrap_or_default();
+    let cli_dupes_importers = reverse_deps
+        .get(&cli_dupes_key)
+        .cloned()
+        .unwrap_or_default();
+
+    assert!(
+        core_dupes_importers.contains(&search_formatters_key),
+        "{core_dupes_importers:?}"
+    );
+    assert!(
+        !cli_dupes_importers.contains(&search_formatters_key),
+        "{cli_dupes_importers:?}"
+    );
+}
diff --git a/crates/fmm-core/src/resolver/mod.rs b/crates/fmm-core/src/resolver/mod.rs
index b2bb579..99cf05c 100644
--- a/crates/fmm-core/src/resolver/mod.rs
+++ b/crates/fmm-core/src/resolver/mod.rs
@@ -23,7 +23,8 @@ pub use go::GoImportResolver;
 pub(crate) use module_hierarchy::is_direct_module_hierarchy_relative;
 pub use rust::RustImportResolver;
 pub(crate) use rust_path::{
-    normal_components, rust_module_name_from_path, rust_module_name_from_specifier,
+    normal_components, relative_importer_starts_with_package_dir, rust_module_name_from_path,
+    rust_module_name_from_specifier,
 };
 
 /// Resolve an import specifier from a source file into an indexed file path.
diff --git a/crates/fmm-core/src/resolver/rust_path.rs b/crates/fmm-core/src/resolver/rust_path.rs
index 119ea13..737c8a3 100644
--- a/crates/fmm-core/src/resolver/rust_path.rs
+++ b/crates/fmm-core/src/resolver/rust_path.rs
@@ -1,6 +1,6 @@
 use std::path::{Component, Path};
 
-pub(super) fn relative_importer_starts_with_package_dir(
+pub(crate) fn relative_importer_starts_with_package_dir(
     importer: &Path,
     package_dir: &Path,
 ) -> bool {