diff --git a/crates/ruff_server/src/lint.rs b/crates/ruff_server/src/lint.rs
index 9b9e8a06d2..36302d6e5f 100644
--- a/crates/ruff_server/src/lint.rs
+++ b/crates/ruff_server/src/lint.rs
@@ -81,13 +81,17 @@ pub(crate) fn check(
             return DiagnosticsMap::default();
         }
 
-        detect_package_root(
-            document_path
-                .parent()
-                .expect("a path to a document should have a parent path"),
-            &settings.linter.namespace_packages,
-        )
-        .map(PackageRoot::root)
+        if let Some(parent) = document_path.parent() {
+            detect_package_root(parent, &settings.linter.namespace_packages).map(PackageRoot::root)
+        } else {
+            // Untitled documents in Neovim are represented using `file:///` URIs which have no
+            // parent. See https://github.com/astral-sh/ruff/issues/15392.
+            tracing::info!(
+                "Cannot detect package root for document with no parent: {:?}",
+                document_path
+            );
+            None
+        }
     } else {
         None
     };
diff --git a/crates/ruff_server/src/session/index.rs b/crates/ruff_server/src/session/index.rs
index 4f75a35fe6..e46984dd0a 100644
--- a/crates/ruff_server/src/session/index.rs
+++ b/crates/ruff_server/src/session/index.rs
@@ -427,12 +427,15 @@ impl WorkspaceSettingsIndex {
         let workspace_url = workspace.url();
         if workspace_url.scheme() != "file" {
             tracing::info!("Ignoring non-file workspace URL: {workspace_url}");
-            show_warn_msg!("Ruff does not support non-file workspaces; Ignoring {workspace_url}");
+            show_warn_msg!("Ruff does not support non-file workspaces; ignoring {workspace_url}");
             return Ok(());
         }
-        let workspace_path = workspace_url.to_file_path().map_err(|()| {
-            anyhow!("Failed to convert workspace URL to file path: {workspace_url}")
-        })?;
+        let Ok(workspace_path) = workspace_url.to_file_path() else {
+            tracing::warn!(
+                "Failed to convert workspace URL to file path; ignoring {workspace_url}"
+            );
+            return Ok(());
+        };
 
         let client_settings = if let Some(workspace_settings) = workspace.settings() {
             ResolvedClientSettings::with_workspace(workspace_settings, global_settings)