diff --git a/src/BlackEditProvider.ts b/src/BlackEditProvider.ts
index 1a00f93..4dfc580 100644
--- a/src/BlackEditProvider.ts
+++ b/src/BlackEditProvider.ts
@@ -32,6 +32,11 @@ export class BlackEditProvider
     implements DocumentRangeFormattingEditProvider, DocumentFormattingEditProvider {
     channel?: OutputChannel;
     hasCompatibleBlackVersion?: boolean;
+    commandPrefix: string;
+
+    constructor(commandPrefix = '') {
+        this.commandPrefix = commandPrefix;
+    }
 
     debug(msg: string, newLine = true) {
         const debug: boolean = workspace.getConfiguration('black', null).get('debug') as boolean;
@@ -79,7 +84,9 @@ export class BlackEditProvider
         const pythonPrefix =
             pythonPath && pythonPath !== 'python' && !hasCustomPath ? `${pythonPath} -m ` : '';
 
-        return `${pythonPrefix}${blackPath} -l ${lineLength}${fast ? ' --fast' : ''} -`;
+        return `${this.commandPrefix}${pythonPrefix}${blackPath} -l ${lineLength}${
+            fast ? ' --fast' : ''
+        } -`;
     }
 
     async provideEdits(
diff --git a/src/extension.ts b/src/extension.ts
index 143ff65..b4cb33b 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -1,3 +1,4 @@
+import { exec } from 'child_process';
 import { Disposable, ExtensionContext, languages, workspace, window } from 'vscode';
 import { BlackEditProvider } from './BlackEditProvider';
 import { blackVersionIsIncompatible } from './utils';
@@ -18,6 +19,7 @@ async function registerFormatter(provider: BlackEditProvider) {
     disposeHandlers();
     languages.registerDocumentFormattingEditProvider('python', provider);
     languages.registerDocumentRangeFormattingEditProvider('python', provider);
+
     // check black version compatibility
     const versionErrorMessage = await blackVersionIsIncompatible(provider);
     if (versionErrorMessage) {
@@ -27,8 +29,30 @@ async function registerFormatter(provider: BlackEditProvider) {
     }
 }
 
-export function activate(context: ExtensionContext) {
-    const provider = new BlackEditProvider();
+export async function activate(context: ExtensionContext) {
+    const providerArgs: string[] = [];
+
+    // workaround for vscode issue: https://github.com/Microsoft/vscode/issues/16261
+    if (process.platform === 'darwin' && !process.env.LANG) {
+        await new Promise((resolve, reject) =>
+            exec(
+                `echo $(defaults read -g AppleLanguages | sed '/"/!d;s/["[:space:]]//g;s/-/_/').UTF-8`,
+                (error, stdout, stderr) => {
+                    // if there's an unexpected error, skip this
+                    if (!error) {
+                        const langCode = stdout.trim();
+                        // make sure stdout matches a valid language code pattern
+                        if (langCode.match(/^[a-z]{2}_[A-Z]{2}\.UTF-8$/)) {
+                            providerArgs.push(`LANG=${langCode} `);
+                        }
+                    }
+                    resolve();
+                }
+            )
+        );
+    }
+
+    const provider = new BlackEditProvider(...providerArgs);
 
     // initial formatter registration
     registerFormatter(provider);
diff --git a/src/test/test-project/.vscode/settings.json b/src/test/test-project/.vscode/settings.json
index 278d6b2..0cbed33 100644
--- a/src/test/test-project/.vscode/settings.json
+++ b/src/test/test-project/.vscode/settings.json
@@ -1,11 +1,11 @@
 {
-    "python.pythonPath": "${workspaceFolder}/.venv/bin/python"
+    "python.pythonPath": "${workspaceFolder}/.venv/bin/python",
     // "python.linting.pylintEnabled": false,
     // "python.linting.flake8Enabled": true,
     // "python.linting.enabled": true,
     // "python.formatting.provider": "none",
     // "black.lineLength": 79,
-    // "black.debug": true,
-    // "black.path": "/Users/brojoe/.pyenv/versions/3.6.3/bin/black",
+    "black.debug": true,
+    "black.path": "/Users/brojoe/.pyenv/versions/3.6.3/bin/black",
     // "python.pythonPath": "${workspaceFolder}/.venv/bin/python",
 }
\ No newline at end of file