diff --git a/cli/lsp/language_server.rs b/cli/lsp/language_server.rs
index 25b588ae6b..27d6e42044 100644
--- a/cli/lsp/language_server.rs
+++ b/cli/lsp/language_server.rs
@@ -771,15 +771,21 @@ impl Inner {
   async fn did_close(&mut self, params: DidCloseTextDocumentParams) {
     let mark = self.performance.mark("did_close", Some(&params));
     if params.text_document.uri.scheme() == "deno" {
-      // we can ignore virtual text documents opening, as they don't need to
+      // we can ignore virtual text documents closing, as they don't need to
       // be tracked in memory, as they are static assets that won't change
       // already managed by the language service
       return;
     }
     let specifier = self.url_map.normalize_url(&params.text_document.uri);
-    self.documents.close(&specifier);
+    let is_diagnosable = self.documents.is_diagnosable(&specifier);
 
-    if self.documents.is_diagnosable(&specifier) {
+    if is_diagnosable {
+      let mut specifiers = self.documents.dependents(&specifier);
+      specifiers.push(specifier.clone());
+      self.diagnostics_server.invalidate(specifiers).await;
+    }
+    self.documents.close(&specifier);
+    if is_diagnosable {
       if let Err(err) = self.diagnostics_server.update() {
         error!("{}", err);
       }
diff --git a/cli/tsc/99_main_compiler.js b/cli/tsc/99_main_compiler.js
index a2f3af176d..f5cfe38dd7 100644
--- a/cli/tsc/99_main_compiler.js
+++ b/cli/tsc/99_main_compiler.js
@@ -75,6 +75,9 @@ delete Object.prototype.__proto__;
   /** @type {Map<string, ts.SourceFile>} */
   const sourceFileCache = new Map();
 
+  /** @type {string[]=} */
+  let scriptFileNamesCache;
+
   /** @type {Map<string, string>} */
   const scriptVersionCache = new Map();
 
@@ -370,7 +373,12 @@ delete Object.prototype.__proto__;
     },
     getScriptFileNames() {
       debug("host.getScriptFileNames()");
-      return core.opSync("op_script_names", undefined);
+      // tsc requests the script file names multiple times even though it can't
+      // possibly have changed, so we will memoize it on a per request basis.
+      if (scriptFileNamesCache) {
+        return scriptFileNamesCache;
+      }
+      return scriptFileNamesCache = core.opSync("op_script_names", undefined);
     },
     getScriptVersion(specifier) {
       debug(`host.getScriptVersion("${specifier}")`);
@@ -378,9 +386,8 @@ delete Object.prototype.__proto__;
       if (sourceFile) {
         return sourceFile.version ?? "1";
       }
-      // tsc neurotically requests the script version multiple times even though
-      // it can't possibly have changed, so we will memoize it on a per request
-      // basis.
+      // tsc requests the script version multiple times even though it can't
+      // possibly have changed, so we will memoize it on a per request basis.
       if (scriptVersionCache.has(specifier)) {
         return scriptVersionCache.get(specifier);
       }
@@ -543,6 +550,8 @@ delete Object.prototype.__proto__;
    */
   function serverRequest({ id, ...request }) {
     debug(`serverRequest()`, { id, ...request });
+    // reset all memoized source files names
+    scriptFileNamesCache = undefined;
     // evict all memoized source file versions
     scriptVersionCache.clear();
     switch (request.method) {