diff --git a/src/snapshots/cargo_mutants__visit__test__expected_mutants_for_own_source_tree.snap b/src/snapshots/cargo_mutants__visit__test__expected_mutants_for_own_source_tree.snap
index 29b73f5d..efa3fa9b 100644
--- a/src/snapshots/cargo_mutants__visit__test__expected_mutants_for_own_source_tree.snap
+++ b/src/snapshots/cargo_mutants__visit__test__expected_mutants_for_own_source_tree.snap
@@ -328,6 +328,8 @@ src/visit.rs: replace attr_is_mutants_skip -> bool with false
 src/workspace.rs: replace <impl Debug for Workspace>::fmt -> fmt::Result with Ok(Default::default())
 src/workspace.rs: replace <impl Debug for Workspace>::fmt -> fmt::Result with Err(::anyhow::anyhow!("mutated!"))
 src/workspace.rs: replace PackageFilter::explicit -> PackageFilter with Default::default()
+src/workspace.rs: replace PackageFilter::matches -> bool with true
+src/workspace.rs: replace PackageFilter::matches -> bool with false
 src/workspace.rs: replace Workspace::open -> Result<Self> with Ok(Default::default())
 src/workspace.rs: replace Workspace::open -> Result<Self> with Err(::anyhow::anyhow!("mutated!"))
 src/workspace.rs: replace Workspace::packages -> Result<Vec<Arc<Package>>> with Ok(vec![])
@@ -344,8 +346,6 @@ src/workspace.rs: replace Workspace::discover -> Result<Discovered> with Err(::a
 src/workspace.rs: replace Workspace::mutants -> Result<Vec<Mutant>> with Ok(vec![])
 src/workspace.rs: replace Workspace::mutants -> Result<Vec<Mutant>> with Ok(vec![Default::default()])
 src/workspace.rs: replace Workspace::mutants -> Result<Vec<Mutant>> with Err(::anyhow::anyhow!("mutated!"))
-src/workspace.rs: replace filter_package_metadata -> Vec<&'m cargo_metadata::Package> with vec![]
-src/workspace.rs: replace filter_package_metadata -> Vec<&'m cargo_metadata::Package> with vec![&Default::default()]
 src/workspace.rs: replace direct_package_sources -> Result<Vec<Utf8PathBuf>> with Ok(vec![])
 src/workspace.rs: replace direct_package_sources -> Result<Vec<Utf8PathBuf>> with Ok(vec![Default::default()])
 src/workspace.rs: replace direct_package_sources -> Result<Vec<Utf8PathBuf>> with Err(::anyhow::anyhow!("mutated!"))
diff --git a/src/workspace.rs b/src/workspace.rs
index 174b50d8..af8adfef 100644
--- a/src/workspace.rs
+++ b/src/workspace.rs
@@ -44,6 +44,16 @@ impl PackageFilter {
     pub fn explicit<S: ToString, I: IntoIterator<Item = S>>(names: I) -> PackageFilter {
         PackageFilter::Explicit(names.into_iter().map(|s| s.to_string()).collect_vec())
     }
+
+    pub fn matches(&self, package_metadata: &cargo_metadata::Package) -> bool {
+        match self {
+            PackageFilter::All => true,
+            PackageFilter::Explicit(include_names) => {
+                include_names.contains(&package_metadata.name)
+            }
+            PackageFilter::Auto(..) => todo!(),
+        }
+    }
 }
 
 /// A package and the top source files within it.
@@ -77,8 +87,11 @@ impl Workspace {
     /// Find all the packages and their top source files.
     fn package_tops(&self, package_filter: &PackageFilter) -> Result<Vec<PackageTop>> {
         let mut tops = Vec::new();
-        for package_metadata in filter_package_metadata(&self.metadata, package_filter)
+        for package_metadata in self
+            .metadata
+            .workspace_packages()
             .into_iter()
+            .filter(|pmeta| package_filter.matches(pmeta))
             .sorted_by_key(|p| &p.name)
         {
             check_interrupted()?;
@@ -160,23 +173,6 @@ impl Workspace {
     }
 }
 
-fn filter_package_metadata<'m>(
-    metadata: &'m cargo_metadata::Metadata,
-    package_filter: &PackageFilter,
-) -> Vec<&'m cargo_metadata::Package> {
-    metadata
-        .workspace_packages()
-        .iter()
-        .filter(move |pmeta| match package_filter {
-            PackageFilter::All => true,
-            PackageFilter::Explicit(include_names) => include_names.contains(&pmeta.name),
-            PackageFilter::Auto(..) => todo!(),
-        })
-        .sorted_by_key(|pm| &pm.name)
-        .copied()
-        .collect()
-}
-
 /// Find all the files that are named in the `path` of targets in a Cargo manifest that should be tested.
 ///
 /// These are the starting points for discovering source files.