diff --git a/CHANGELOG.md b/CHANGELOG.md
index 898393cbc..296ef4575 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@
 - Potential race condition in incremental compilation. https://github.com/rescript-lang/rescript-vscode/pull/1167
 - Fix extension crash triggered by incremental compilation. https://github.com/rescript-lang/rescript-vscode/pull/1169
 - Fix file watchers on Windows when using WSL. https://github.com/rescript-lang/rescript-vscode/pull/1178
+- Fix empty completion in rescript@13.0.0-alpha.5. https://github.com/rescript-lang/rescript-vscode/pull/1188
 
 #### :nail_care: Polish
 
diff --git a/server/src/server.ts b/server/src/server.ts
index f4829dd0e..23ccd9602 100644
--- a/server/src/server.ts
+++ b/server/src/server.ts
@@ -623,7 +623,7 @@ async function hover(msg: p.RequestMessage) {
     params.textDocument.uri as utils.FileURI,
   );
   let code = getOpenedFileContent(params.textDocument.uri as utils.FileURI);
-  let tmpname = utils.createFileInTempDir();
+  let tmpname = utils.createFileInTempDir(utils.getExtension(filePath));
   fs.writeFileSync(tmpname, code, { encoding: "utf-8" });
   let response = await utils.runAnalysisCommand(
     filePath,
@@ -699,7 +699,7 @@ async function signatureHelp(msg: p.RequestMessage) {
     params.textDocument.uri as utils.FileURI,
   );
   let code = getOpenedFileContent(params.textDocument.uri as utils.FileURI);
-  let tmpname = utils.createFileInTempDir();
+  let tmpname = utils.createFileInTempDir(utils.getExtension(filePath));
   fs.writeFileSync(tmpname, code, { encoding: "utf-8" });
   let response = await utils.runAnalysisCommand(
     filePath,
@@ -871,9 +871,8 @@ async function documentSymbol(msg: p.RequestMessage) {
   let filePath = utils.uriToNormalizedPath(
     params.textDocument.uri as utils.FileURI,
   );
-  let extension = path.extname(params.textDocument.uri);
   let code = getOpenedFileContent(params.textDocument.uri as utils.FileURI);
-  let tmpname = utils.createFileInTempDir(extension);
+  let tmpname = utils.createFileInTempDir(utils.getExtension(filePath));
   fs.writeFileSync(tmpname, code, { encoding: "utf-8" });
   let response = await utils.runAnalysisCommand(
     filePath,
@@ -909,9 +908,8 @@ async function semanticTokens(msg: p.RequestMessage) {
   let filePath = utils.uriToNormalizedPath(
     params.textDocument.uri as utils.FileURI,
   );
-  let extension = path.extname(params.textDocument.uri);
   let code = getOpenedFileContent(params.textDocument.uri as utils.FileURI);
-  let tmpname = utils.createFileInTempDir(extension);
+  let tmpname = utils.createFileInTempDir(utils.getExtension(filePath));
   fs.writeFileSync(tmpname, code, { encoding: "utf-8" });
   let response = await utils.runAnalysisCommand(
     filePath,
@@ -930,7 +928,7 @@ async function completion(msg: p.RequestMessage) {
     params.textDocument.uri as utils.FileURI,
   );
   let code = getOpenedFileContent(params.textDocument.uri as utils.FileURI);
-  let tmpname = utils.createFileInTempDir();
+  let tmpname = utils.createFileInTempDir(utils.getExtension(filePath));
   fs.writeFileSync(tmpname, code, { encoding: "utf-8" });
   let response = await utils.runAnalysisCommand(
     filePath,
@@ -978,8 +976,7 @@ async function codeAction(msg: p.RequestMessage): Promise<p.ResponseMessage> {
     params.textDocument.uri as utils.FileURI,
   );
   let code = getOpenedFileContent(params.textDocument.uri as utils.FileURI);
-  let extension = path.extname(params.textDocument.uri);
-  let tmpname = utils.createFileInTempDir(extension);
+  let tmpname = utils.createFileInTempDir(utils.getExtension(filePath));
 
   // Check local code actions coming from the diagnostics, or from incremental compilation.
   let localResults: v.CodeAction[] = [];
@@ -1102,8 +1099,7 @@ let updateDiagnosticSyntax = async (
     return;
   }
   let filePath = utils.uriToNormalizedPath(fileUri);
-  let extension = path.extname(filePath);
-  let tmpname = utils.createFileInTempDir(extension);
+  let tmpname = utils.createFileInTempDir(utils.getExtension(filePath));
   fs.writeFileSync(tmpname, fileContent, { encoding: "utf-8" });
 
   // We need to account for any existing diagnostics from the compiler for this
diff --git a/server/src/utils.ts b/server/src/utils.ts
index e249f3398..e4c34e256 100644
--- a/server/src/utils.ts
+++ b/server/src/utils.ts
@@ -82,6 +82,10 @@ export function uriToNormalizedPath(uri: FileURI): NormalizedPath {
 let tempFilePrefix = "rescript_format_file_" + process.pid + "_";
 let tempFileId = 0;
 
+export function getExtension(filePath: NormalizedPath): string {
+  return path.extname(filePath);
+}
+
 export let createFileInTempDir = (extension = ""): NormalizedPath => {
   let tempFileName = tempFilePrefix + tempFileId + extension;
   tempFileId = tempFileId + 1;