diff --git a/packages/core/src/input/InputFileResolver.ts b/packages/core/src/input/InputFileResolver.ts
index 340e616afc..17c7b74a43 100644
--- a/packages/core/src/input/InputFileResolver.ts
+++ b/packages/core/src/input/InputFileResolver.ts
@@ -3,7 +3,7 @@ import * as path from 'path';
 import fs = require('fs');
 
 import { from } from 'rxjs';
-import { filter, mergeMap, toArray } from 'rxjs/operators';
+import { filter, map, mergeMap, toArray } from 'rxjs/operators';
 import { File, StrykerOptions } from '@stryker-mutator/api/core';
 import { Logger } from '@stryker-mutator/api/logging';
 import { commonTokens, tokens } from '@stryker-mutator/api/plugin';
@@ -163,7 +163,9 @@ export default class InputFileResolver {
       .pipe(
         mergeMap((fileName) => this.readFile(fileName), MAX_CONCURRENT_FILE_IO),
         filter(notEmpty),
-        toArray()
+        toArray(),
+        // Filter the files here, so we force a deterministic instrumentation process
+        map((files) => files.sort((a, b) => (a.name < b.name ? -1 : a.name > b.name ? 1 : 0)))
       )
       .toPromise();
     return files;
diff --git a/packages/core/test/integration/input/InputFileResolver.it.spec.ts b/packages/core/test/integration/input/InputFileResolver.it.spec.ts
index c4a8d36d39..0f464608c7 100644
--- a/packages/core/test/integration/input/InputFileResolver.it.spec.ts
+++ b/packages/core/test/integration/input/InputFileResolver.it.spec.ts
@@ -32,8 +32,7 @@ describe(`${InputFileResolver.name} integration`, () => {
   it('should by default resolve reasonable project source files to be mutated', async () => {
     process.chdir(resolveTestResource());
     const inputFiles = await sut.resolve();
-    // eslint-disable-next-line @typescript-eslint/require-array-sort-compare
-    expect(inputFiles.filesToMutate.map((file) => file.name).sort()).deep.eq([
+    expect(inputFiles.filesToMutate.map((file) => file.name)).deep.eq([
       resolveTestResource('lib', 'string-utils.js'),
       resolveTestResource('src', 'app.ts'),
       resolveTestResource('src', 'components', 'calculator', 'calculator.component.tsx'),
diff --git a/packages/core/test/unit/input/InputFileResolver.spec.ts b/packages/core/test/unit/input/InputFileResolver.spec.ts
index d2a1ba193e..150ad62bad 100644
--- a/packages/core/test/unit/input/InputFileResolver.spec.ts
+++ b/packages/core/test/unit/input/InputFileResolver.spec.ts
@@ -147,9 +147,9 @@ describe(InputFileResolver.name, () => {
     });
     const files = await sut.resolve();
     assertions.expectTextFilesEqual(files.files, [
-      new File(path.resolve('å.js'), ''),
-      new File(path.resolve('src/🐱‍👓ninja.cat.js'), ''),
       new File(path.resolve('a\\test\\file.js'), ''),
+      new File(path.resolve('src/🐱‍👓ninja.cat.js'), ''),
+      new File(path.resolve('å.js'), ''),
     ]);
   });
 
@@ -199,10 +199,10 @@ describe(InputFileResolver.name, () => {
       expect(result.filesToMutate.map((_) => _.name)).to.deep.equal([path.resolve('/mute1.js'), path.resolve('/mute2.js')]);
       expect(result.files.map((file) => file.name)).to.deep.equal([
         path.resolve('/file1.js'),
-        path.resolve('/mute1.js'),
         path.resolve('/file2.js'),
-        path.resolve('/mute2.js'),
         path.resolve('/file3.js'),
+        path.resolve('/mute1.js'),
+        path.resolve('/mute2.js'),
       ]);
     });
 
@@ -221,10 +221,10 @@ describe(InputFileResolver.name, () => {
       await sut.resolve();
       const expected: SourceFile[] = [
         { path: path.resolve('/file1.js'), content: 'file 1 content' },
-        { path: path.resolve('/mute1.js'), content: 'mutate 1 content' },
         { path: path.resolve('/file2.js'), content: 'file 2 content' },
-        { path: path.resolve('/mute2.js'), content: 'mutate 2 content' },
         { path: path.resolve('/file3.js'), content: 'file 3 content' },
+        { path: path.resolve('/mute1.js'), content: 'mutate 1 content' },
+        { path: path.resolve('/mute2.js'), content: 'mutate 2 content' },
       ];
       expect(reporterMock.onAllSourceFilesRead).calledWith(expected);
     });
@@ -236,10 +236,10 @@ describe(InputFileResolver.name, () => {
       await sut.resolve();
       const expected: SourceFile[] = [
         { path: path.resolve('/file1.js'), content: 'file 1 content' },
-        { path: path.resolve('/mute1.js'), content: 'mutate 1 content' },
         { path: path.resolve('/file2.js'), content: 'file 2 content' },
-        { path: path.resolve('/mute2.js'), content: 'mutate 2 content' },
         { path: path.resolve('/file3.js'), content: 'file 3 content' },
+        { path: path.resolve('/mute1.js'), content: 'mutate 1 content' },
+        { path: path.resolve('/mute2.js'), content: 'mutate 2 content' },
       ];
       expected.forEach((sourceFile) => expect(reporterMock.onSourceFileRead).calledWith(sourceFile));
     });
@@ -333,7 +333,7 @@ describe(InputFileResolver.name, () => {
     it('should order files by expression order', async () => {
       testInjector.options.files = ['file2', 'file*'];
       const result = await createSut().resolve();
-      assertFilesEqual(result.files, files(['/file2.js', 'file 2 content'], ['/file1.js', 'file 1 content'], ['/file3.js', 'file 3 content']));
+      assertFilesEqual(result.files, files(['/file1.js', 'file 1 content'], ['/file2.js', 'file 2 content'], ['/file3.js', 'file 3 content']));
     });
   });