diff --git a/crates/rust-analyzer/src/diagnostics.rs b/crates/rust-analyzer/src/diagnostics.rs
index 03294e5ab3..e64a15ae04 100644
--- a/crates/rust-analyzer/src/diagnostics.rs
+++ b/crates/rust-analyzer/src/diagnostics.rs
@@ -15,7 +15,7 @@ use triomphe::Arc;
 use crate::{global_state::GlobalStateSnapshot, lsp, lsp_ext, main_loop::DiagnosticsTaskKind};
 
 pub(crate) type CheckFixes =
-    Arc<IntMap<usize, FxHashMap<Option<PackageId>, IntMap<FileId, Vec<Fix>>>>>;
+    Arc<IntMap<usize, FxHashMap<Option<Arc<PackageId>>, IntMap<FileId, Vec<Fix>>>>>;
 
 #[derive(Debug, Default, Clone)]
 pub struct DiagnosticsMapConfig {
@@ -33,8 +33,10 @@ pub(crate) struct DiagnosticCollection {
     pub(crate) native_syntax: IntMap<FileId, (DiagnosticsGeneration, Vec<lsp_types::Diagnostic>)>,
     pub(crate) native_semantic: IntMap<FileId, (DiagnosticsGeneration, Vec<lsp_types::Diagnostic>)>,
     // FIXME: should be Vec<flycheck::Diagnostic>
-    pub(crate) check:
-        IntMap<usize, FxHashMap<Option<PackageId>, IntMap<FileId, Vec<lsp_types::Diagnostic>>>>,
+    pub(crate) check: IntMap<
+        usize,
+        FxHashMap<Option<Arc<PackageId>>, IntMap<FileId, Vec<lsp_types::Diagnostic>>>,
+    >,
     pub(crate) check_fixes: CheckFixes,
     changes: IntSet<FileId>,
     /// Counter for supplying a new generation number for diagnostics.
@@ -74,7 +76,11 @@ impl DiagnosticCollection {
         self.changes.insert(file_id);
     }
 
-    pub(crate) fn clear_check_for_package(&mut self, flycheck_id: usize, package_id: PackageId) {
+    pub(crate) fn clear_check_for_package(
+        &mut self,
+        flycheck_id: usize,
+        package_id: Arc<PackageId>,
+    ) {
         let Some(check) = self.check.get_mut(&flycheck_id) else {
             return;
         };
@@ -84,7 +90,7 @@ impl DiagnosticCollection {
     pub(crate) fn add_check_diagnostic(
         &mut self,
         flycheck_id: usize,
-        package_id: &Option<PackageId>,
+        package_id: &Option<Arc<PackageId>>,
         file_id: FileId,
         diagnostic: lsp_types::Diagnostic,
         fix: Option<Box<Fix>>,
diff --git a/crates/rust-analyzer/src/flycheck.rs b/crates/rust-analyzer/src/flycheck.rs
index d178b8b1fd..7ff36deb98 100644
--- a/crates/rust-analyzer/src/flycheck.rs
+++ b/crates/rust-analyzer/src/flycheck.rs
@@ -1,7 +1,7 @@
 //! Flycheck provides the functionality needed to run `cargo check` to provide
 //! LSP diagnostics based on the output of the command.
 
-use std::{fmt, io, mem, process::Command, sync::Arc, time::Duration};
+use std::{fmt, io, mem, process::Command, time::Duration};
 
 use cargo_metadata::PackageId;
 use crossbeam_channel::{select_biased, unbounded, Receiver, Sender};
@@ -13,6 +13,7 @@ pub(crate) use cargo_metadata::diagnostic::{
     Applicability, Diagnostic, DiagnosticCode, DiagnosticLevel, DiagnosticSpan,
 };
 use toolchain::Tool;
+use triomphe::Arc;
 
 use crate::command::{CommandHandle, ParseFromLine};
 
@@ -155,14 +156,14 @@ pub(crate) enum FlycheckMessage {
         id: usize,
         workspace_root: Arc<AbsPathBuf>,
         diagnostic: Diagnostic,
-        package_id: Option<PackageId>,
+        package_id: Option<Arc<PackageId>>,
     },
 
     /// Request clearing all outdated diagnostics.
     ClearDiagnostics {
         id: usize,
         /// The package whose diagnostics to clear, or if unspecified, all diagnostics.
-        package_id: Option<PackageId>,
+        package_id: Option<Arc<PackageId>>,
     },
 
     /// Request check progress notification to client
@@ -229,7 +230,7 @@ struct FlycheckActor {
     command_handle: Option<CommandHandle<CargoCheckMessage>>,
     /// The receiver side of the channel mentioned above.
     command_receiver: Option<Receiver<CargoCheckMessage>>,
-    package_status: FxHashMap<PackageId, DiagnosticReceived>,
+    package_status: FxHashMap<Arc<PackageId>, DiagnosticReceived>,
 }
 
 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
@@ -370,7 +371,9 @@ impl FlycheckActor {
                             "artifact received"
                         );
                         self.report_progress(Progress::DidCheckCrate(msg.target.name));
-                        self.package_status.entry(msg.package_id).or_insert(DiagnosticReceived::No);
+                        self.package_status
+                            .entry(Arc::new(msg.package_id))
+                            .or_insert(DiagnosticReceived::No);
                     }
                     CargoCheckMessage::Diagnostic { diagnostic, package_id } => {
                         tracing::trace!(
@@ -517,7 +520,7 @@ impl FlycheckActor {
 #[allow(clippy::large_enum_variant)]
 enum CargoCheckMessage {
     CompilerArtifact(cargo_metadata::Artifact),
-    Diagnostic { diagnostic: Diagnostic, package_id: Option<PackageId> },
+    Diagnostic { diagnostic: Diagnostic, package_id: Option<Arc<PackageId>> },
 }
 
 impl ParseFromLine for CargoCheckMessage {
@@ -534,7 +537,7 @@ impl ParseFromLine for CargoCheckMessage {
                     cargo_metadata::Message::CompilerMessage(msg) => {
                         Some(CargoCheckMessage::Diagnostic {
                             diagnostic: msg.message,
-                            package_id: Some(msg.package_id),
+                            package_id: Some(Arc::new(msg.package_id)),
                         })
                     }
                     _ => None,