diff --git a/lib/dependencies/sub-process.ts b/lib/dependencies/sub-process.ts
index 20078ef6..7e1ed785 100644
--- a/lib/dependencies/sub-process.ts
+++ b/lib/dependencies/sub-process.ts
@@ -15,7 +15,7 @@ function makeSpawnOptions(options?: ProcessOptions) {
     spawnOptions.cwd = options.cwd;
   }
   if (options && options.env) {
-    spawnOptions.env = options.env;
+    spawnOptions.env = { ...options.env };
   }
 
   // Before spawning an external process, we look if we need to restore the system proxy configuration,
diff --git a/test/unit/sub-process.spec.ts b/test/unit/sub-process.spec.ts
new file mode 100644
index 00000000..50f6d09b
--- /dev/null
+++ b/test/unit/sub-process.spec.ts
@@ -0,0 +1,92 @@
+import { executeSync } from '../../lib/dependencies/sub-process';
+
+describe('Test sub-process.ts', () => {
+  it('test restoring proxy setting in executeSync()', async () => {
+    const expectedProxy = 'proxy';
+    const expectedProxyHTTPS = 'proxy2';
+    const expectedNoProxy = 'no-proxy';
+
+    process.env.SNYK_SYSTEM_HTTP_PROXY = 'http://127.0.0.1:3128';
+    process.env.SNYK_SYSTEM_HTTPS_PROXY = 'http://127.0.0.1:3129';
+    process.env.SNYK_SYSTEM_NO_PROXY = 'something.com';
+
+    const options = {
+      env: {
+        HTTP_PROXY: expectedProxy,
+        HTTPS_PROXY: expectedProxyHTTPS,
+        NO_PROXY: expectedNoProxy,
+      },
+    };
+
+    let output = executeSync(
+      'python3',
+      ['-c', "import os; print(os.environ['HTTP_PROXY'])"],
+      options
+    );
+    expect(output.stdout.toString().trim()).toEqual(
+      process.env.SNYK_SYSTEM_HTTP_PROXY
+    );
+
+    output = executeSync(
+      'python3',
+      ['-c', "import os; print(os.environ['HTTPS_PROXY'])"],
+      options
+    );
+    expect(output.stdout.toString().trim()).toEqual(
+      process.env.SNYK_SYSTEM_HTTPS_PROXY
+    );
+
+    output = executeSync(
+      'python3',
+      ['-c', "import os; print(os.environ['NO_PROXY'])"],
+      options
+    );
+    expect(output.stdout.toString().trim()).toEqual(
+      process.env.SNYK_SYSTEM_NO_PROXY
+    );
+
+    // ensure that options remain unchanged
+    expect(options.env.HTTP_PROXY).toEqual(expectedProxy);
+    expect(options.env.HTTPS_PROXY).toEqual(expectedProxyHTTPS);
+    expect(options.env.NO_PROXY).toEqual(expectedNoProxy);
+
+    delete process.env.SNYK_SYSTEM_HTTP_PROXY;
+    delete process.env.SNYK_SYSTEM_HTTPS_PROXY;
+    delete process.env.SNYK_SYSTEM_NO_PROXY;
+  });
+
+  it('test executeSync()', async () => {
+    const expectedProxy = 'proxy';
+    const expectedProxyHTTPS = 'proxy2';
+    const expectedNoProxy = 'no-proxy';
+
+    const options = {
+      env: {
+        HTTP_PROXY: expectedProxy,
+        HTTPS_PROXY: expectedProxyHTTPS,
+        NO_PROXY: expectedNoProxy,
+      },
+    };
+
+    let output = executeSync(
+      'python3',
+      ['-c', "import os; print(os.environ['HTTP_PROXY'])"],
+      options
+    );
+    expect(output.stdout.toString().trim()).toEqual(expectedProxy);
+
+    output = executeSync(
+      'python3',
+      ['-c', "import os; print(os.environ['HTTPS_PROXY'])"],
+      options
+    );
+    expect(output.stdout.toString().trim()).toEqual(expectedProxyHTTPS);
+
+    output = executeSync(
+      'python3',
+      ['-c', "import os; print(os.environ['NO_PROXY'])"],
+      options
+    );
+    expect(output.stdout.toString().trim()).toEqual(expectedNoProxy);
+  });
+});