diff --git a/packages/stryker/src/isolated-runner/IsolatedTestRunnerAdapter.ts b/packages/stryker/src/isolated-runner/IsolatedTestRunnerAdapter.ts
index f83bb722eb..7183d74df9 100644
--- a/packages/stryker/src/isolated-runner/IsolatedTestRunnerAdapter.ts
+++ b/packages/stryker/src/isolated-runner/IsolatedTestRunnerAdapter.ts
@@ -116,7 +116,7 @@ export default class TestRunnerChildProcessAdapter extends EventEmitter implemen
     this.currentTask = new DisposeTask(MAX_WAIT_FOR_DISPOSE);
     this.sendDisposeCommand();
     return this.currentTask.promise
-      .then(() => this.workerProcess.kill('SIGKILL'));
+      .then(() => this.workerProcess.kill());
   }
 
   private sendRunCommand(options: RunOptions) {
diff --git a/packages/stryker/test/unit/isolated-runner/IsolatedTestRunnerAdapterSpec.ts b/packages/stryker/test/unit/isolated-runner/IsolatedTestRunnerAdapterSpec.ts
index 12639a38e4..609c0dd891 100644
--- a/packages/stryker/test/unit/isolated-runner/IsolatedTestRunnerAdapterSpec.ts
+++ b/packages/stryker/test/unit/isolated-runner/IsolatedTestRunnerAdapterSpec.ts
@@ -124,15 +124,17 @@ describe('IsolatedTestRunnerAdapter', () => {
         return expect(fakeChildProcess.send).to.have.been.calledWith(serialize({ kind: 'dispose' }));
       });
 
-      describe('and child process responses to dispose', () => {
+      describe('and child process responds to dispose', () => {
         beforeEach(() => {
           const promise = sut.dispose();
           receiveMessage({ kind: 'disposeDone' });
           return promise;
         });
 
-        it('should kill the child process', () =>
-          expect(fakeChildProcess.kill).to.have.been.calledWith());
+        it('should kill the child process', () => {
+          expect(fakeChildProcess.kill).to.not.have.been.calledWith('SIGKILL');
+          expect(fakeChildProcess.kill).to.have.been.called;
+        });
       });
 
       describe('and a timeout occurred', () => {
@@ -144,8 +146,10 @@ describe('IsolatedTestRunnerAdapter', () => {
           return promise;
         });
 
-        it('should kill the child process', () =>
-          expect(fakeChildProcess.kill).to.have.been.calledWith('SIGKILL'));
+        it('should kill the child process', () => {
+          expect(fakeChildProcess.kill).to.not.have.been.calledWith('SIGKILL');
+          expect(fakeChildProcess.kill).to.have.been.called;
+        });
       });
     });
     it('should reject any exceptions', () => {