diff --git a/packages/typescript-estree/src/create-program/createWatchProgram.ts b/packages/typescript-estree/src/create-program/createWatchProgram.ts
index 9223107986af..38bd209ff3f2 100644
--- a/packages/typescript-estree/src/create-program/createWatchProgram.ts
+++ b/packages/typescript-estree/src/create-program/createWatchProgram.ts
@@ -1,6 +1,5 @@
 import debug from 'debug';
 import fs from 'fs';
-import path from 'path';
 import * as ts from 'typescript'; // leave this as * as ts so people using util package don't need syntheticDefaultImports
 import { Extra } from '../parser-options';
 import { WatchCompilerHostOfConfigFile } from './WatchCompilerHostOfConfigFile';
@@ -67,7 +66,7 @@ function saveWatchCallback(
     fileName: string,
     callback: ts.FileWatcherCallback,
   ): ts.FileWatcher => {
-    const normalizedFileName = getCanonicalFileName(path.normalize(fileName));
+    const normalizedFileName = getCanonicalFileName(fileName);
     const watchers = ((): Set<ts.FileWatcherCallback> => {
       let watchers = trackingMap.get(normalizedFileName);
       if (!watchers) {
@@ -246,8 +245,7 @@ function createWatchProgram(
   watchCompilerHost.readFile = (filePathIn, encoding): string | undefined => {
     const filePath = getCanonicalFileName(filePathIn);
     const fileContent =
-      path.normalize(filePath) ===
-      path.normalize(currentLintOperationState.filePath)
+      filePath === currentLintOperationState.filePath
         ? currentLintOperationState.code
         : oldReadFile(filePath, encoding);
     if (fileContent) {
diff --git a/packages/typescript-estree/src/create-program/shared.ts b/packages/typescript-estree/src/create-program/shared.ts
index 6509997094f9..a19bef274139 100644
--- a/packages/typescript-estree/src/create-program/shared.ts
+++ b/packages/typescript-estree/src/create-program/shared.ts
@@ -20,14 +20,21 @@ const DEFAULT_COMPILER_OPTIONS: ts.CompilerOptions = {
 
 // This narrows the type so we can be sure we're passing canonical names in the correct places
 type CanonicalPath = string & { __brand: unknown };
+
 // typescript doesn't provide a ts.sys implementation for browser environments
 const useCaseSensitiveFileNames =
   ts.sys !== undefined ? ts.sys.useCaseSensitiveFileNames : true;
-const getCanonicalFileName = useCaseSensitiveFileNames
-  ? (filePath: string): CanonicalPath =>
-      path.normalize(filePath) as CanonicalPath
-  : (filePath: string): CanonicalPath =>
-      path.normalize(filePath).toLowerCase() as CanonicalPath;
+const correctPathCasing = useCaseSensitiveFileNames
+  ? (filePath: string): string => filePath
+  : (filePath: string): string => filePath.toLowerCase();
+
+function getCanonicalFileName(filePath: string): CanonicalPath {
+  let normalized = path.normalize(filePath);
+  if (normalized.endsWith('/')) {
+    normalized = normalized.substr(0, normalized.length - 1);
+  }
+  return correctPathCasing(normalized) as CanonicalPath;
+}
 
 function getTsconfigPath(tsconfigPath: string, extra: Extra): CanonicalPath {
   return getCanonicalFileName(
diff --git a/packages/typescript-estree/tests/lib/persistentParse.ts b/packages/typescript-estree/tests/lib/persistentParse.ts
index e1cb8b9f9b76..502245977bdc 100644
--- a/packages/typescript-estree/tests/lib/persistentParse.ts
+++ b/packages/typescript-estree/tests/lib/persistentParse.ts
@@ -3,14 +3,6 @@ import path from 'path';
 import tmp from 'tmp';
 import { clearCaches, parseAndGenerateServices } from '../../src/parser';
 
-const tsConfigExcludeBar = {
-  include: ['src'],
-  exclude: ['./src/bar.ts'],
-};
-const tsConfigIncludeAll = {
-  include: ['src'],
-  exclude: [],
-};
 const CONTENTS = {
   foo: 'console.log("foo")',
   bar: 'console.log("bar")',
@@ -69,7 +61,10 @@ function parseFile(filename: 'foo' | 'bar' | 'baz/bar', tmpDir: string): void {
   });
 }
 
-describe('persistent lint session', () => {
+function baseTests(
+  tsConfigExcludeBar: Record<string, unknown>,
+  tsConfigIncludeAll: Record<string, unknown>,
+): void {
   it('parses both files successfully when included', () => {
     const PROJECT_DIR = setup(tsConfigIncludeAll);
 
@@ -175,4 +170,48 @@ describe('persistent lint session', () => {
   });
 
   // TODO - support the complex monorepo case with a tsconfig with no include/exclude
+}
+
+describe('persistent parse', () => {
+  describe('includes not ending in a slash', () => {
+    const tsConfigExcludeBar = {
+      include: ['src'],
+      exclude: ['./src/bar.ts'],
+    };
+    const tsConfigIncludeAll = {
+      include: ['src'],
+      exclude: [],
+    };
+
+    baseTests(tsConfigExcludeBar, tsConfigIncludeAll);
+  });
+
+  /*
+  If the includes ends in a slash, typescript will ask for watchers ending in a slash.
+  These tests ensure the normalisation code works as expected in this case.
+  */
+  describe('includes ending in a slash', () => {
+    const tsConfigExcludeBar = {
+      include: ['src/'],
+      exclude: ['./src/bar.ts'],
+    };
+    const tsConfigIncludeAll = {
+      include: ['src/'],
+      exclude: [],
+    };
+
+    baseTests(tsConfigExcludeBar, tsConfigIncludeAll);
+  });
+
+  /*
+  If there is no includes, then typescript will ask for a slightly different set of watchers.
+  */
+  describe('tsconfig with no includes / files', () => {
+    const tsConfigExcludeBar = {
+      exclude: ['./src/bar.ts'],
+    };
+    const tsConfigIncludeAll = {};
+
+    baseTests(tsConfigExcludeBar, tsConfigIncludeAll);
+  });
 });