diff --git a/crates/project/src/lsp_store.rs b/crates/project/src/lsp_store.rs
index 00d26652c2b0d9ef5aaab1e70f6c519365588537..d007bd7b21881a47637f5bfbfa8ac510e3ee1eb3 100644
--- a/crates/project/src/lsp_store.rs
+++ b/crates/project/src/lsp_store.rs
@@ -249,6 +249,21 @@ pub struct DocumentDiagnostics {
     version: Option<i32>,
 }
 
+#[cfg(test)]
+impl DocumentDiagnostics {
+    pub fn new(
+        diagnostics: Vec<DiagnosticEntry<Unclipped<PointUtf16>>>,
+        document_abs_path: PathBuf,
+        version: Option<i32>,
+    ) -> Self {
+        Self {
+            diagnostics,
+            document_abs_path,
+            version,
+        }
+    }
+}
+
 #[derive(Default, Debug)]
 struct DynamicRegistrations {
     did_change_watched_files: HashMap<String, Vec<FileSystemWatcher>>,
@@ -2460,7 +2475,10 @@ impl LocalLspStore {
         for (new_diagnostic, entry) in diagnostics {
             let start;
             let end;
-            if new_diagnostic && entry.diagnostic.is_disk_based {
+            if entry.diagnostic.is_disk_based {
+                if !new_diagnostic {
+                    continue;
+                }
                 // Some diagnostics are based on files on disk instead of buffers'
                 // current contents. Adjust these diagnostics' ranges to reflect
                 // any unsaved edits.
diff --git a/crates/project/src/project_tests.rs b/crates/project/src/project_tests.rs
index af459c29f1dde1e711ea2e18873a62497f065784..a7a1b32317a0787fab22a9507c364e85d07387f0 100644
--- a/crates/project/src/project_tests.rs
+++ b/crates/project/src/project_tests.rs
@@ -3,6 +3,7 @@
 use crate::{
     Event,
     git_store::{GitStoreEvent, RepositoryEvent, StatusEntry, pending_op},
+    lsp_store::{DocumentDiagnostics, DocumentDiagnosticsUpdate},
     task_inventory::TaskContexts,
     task_store::TaskSettingsLocation,
     *,
@@ -2878,6 +2879,96 @@ async fn test_diagnostics_from_multiple_language_servers(cx: &mut gpui::TestAppC
     });
 }
 
+#[gpui::test]
+async fn test_disk_based_diagnostics_not_reused(cx: &mut gpui::TestAppContext) {
+    init_test(cx);
+
+    let fs = FakeFs::new(cx.executor());
+    fs.insert_tree(path!("/dir"), json!({ "a.rs": "fn a() { A }" }))
+        .await;
+
+    let project = Project::test(fs, [Path::new(path!("/dir"))], cx).await;
+    let lsp_store = project.read_with(cx, |project, _| project.lsp_store.clone());
+    let buffer = project
+        .update(cx, |project, cx| {
+            project.open_local_buffer(path!("/dir/a.rs"), cx)
+        })
+        .await
+        .unwrap();
+
+    // Setup an initial disk-based diagnostic, which will later become old, so
+    // we can later assert that it is ignored when merging diagnostic entries.
+    let diagnostic = DiagnosticEntry {
+        range: Unclipped(PointUtf16::new(0, 9))..Unclipped(PointUtf16::new(0, 10)),
+        diagnostic: Diagnostic {
+            is_disk_based: true,
+            ..Diagnostic::default()
+        },
+    };
+    let diagnostic_update = DocumentDiagnosticsUpdate {
+        diagnostics: DocumentDiagnostics::new(
+            vec![diagnostic],
+            PathBuf::from(path!("/dir/a.rs")),
+            None,
+        ),
+        result_id: None,
+        server_id: LanguageServerId(0),
+        disk_based_sources: Cow::Borrowed(&[]),
+        registration_id: None,
+    };
+    lsp_store.update(cx, |lsp_store, cx| {
+        lsp_store
+            .merge_diagnostic_entries(vec![diagnostic_update], |_, _, _| false, cx)
+            .unwrap();
+    });
+
+    // Quick sanity check, ensure that the initial diagnostic is part of the
+    // buffer's diagnostics.
+    buffer.update(cx, |buffer, _| {
+        let snapshot = buffer.snapshot();
+        let diagnostics: Vec<_> = snapshot
+            .diagnostics_in_range::<_, Point>(0..buffer.len(), false)
+            .collect();
+
+        assert_eq!(diagnostics.len(), 1);
+    });
+
+    // We'll now merge the diagnostic entries with a new diagnostic update, with
+    // no diagnostics. This time around, the `merge` closure will return `true`
+    // to ensure that old diagnostics are retained, ensuring that the first
+    // diagnostic does get added to the full list of diagnostics, even though
+    // it'll later be ignored.
+    let diagnostic_update = lsp_store::DocumentDiagnosticsUpdate {
+        diagnostics: lsp_store::DocumentDiagnostics::new(
+            vec![],
+            PathBuf::from(path!("/dir/a.rs")),
+            None,
+        ),
+        result_id: None,
+        server_id: LanguageServerId(0),
+        disk_based_sources: Cow::Borrowed(&[]),
+        registration_id: None,
+    };
+    lsp_store.update(cx, |lsp_store, cx| {
+        lsp_store
+            .merge_diagnostic_entries(vec![diagnostic_update], |_, _, _| true, cx)
+            .unwrap();
+    });
+
+    // We can now assert that the initial, disk-based diagnostic has been
+    // removed from the buffer's diagnostics, even if the `merge` closure
+    // returned `true`, informing that the old diagnostic could be reused.
+    // The old disk-based diagnostic should be gone, NOT retained
+    buffer.update(cx, |buffer, _| {
+        let snapshot = buffer.snapshot();
+        let diagnostics: Vec<_> = snapshot
+            .diagnostics_in_range::<_, Point>(0..buffer.len(), false)
+            .collect();
+
+        assert_eq!(diagnostics.len(), 0);
+    });
+}
+
 #[gpui::test]
 async fn test_edits_from_lsp2_with_past_version(cx: &mut gpui::TestAppContext) {
     init_test(cx);