diff --git a/src/tsconfig.strictNullChecks.json b/src/tsconfig.strictNullChecks.json
index 7a8cbd429dc..41a010ea970 100644
--- a/src/tsconfig.strictNullChecks.json
+++ b/src/tsconfig.strictNullChecks.json
@@ -64,6 +64,7 @@
 		"./vs/base/common/json.ts",
 		"./vs/base/common/jsonEdit.ts",
 		"./vs/base/common/jsonFormatter.ts",
+		"./vs/base/common/paths.ts",
 		"./vs/base/common/uriIpc.ts",
 		"./vs/base/node/console.ts",
 		"./vs/base/node/crypto.ts",
@@ -73,6 +74,7 @@
 		"./vs/base/node/flow.ts",
 		"./vs/base/node/id.ts",
 		"./vs/base/node/paths.ts",
+		"./vs/base/node/paths.ts",
 		"./vs/base/node/pfs.ts",
 		"./vs/base/node/ports.ts",
 		"./vs/base/node/processes.ts",
@@ -97,6 +99,7 @@
 		"./vs/base/test/common/json.test.ts",
 		"./vs/base/test/common/jsonEdit.test.ts",
 		"./vs/base/test/common/jsonFormatter.test.ts",
+		"./vs/base/test/common/paths.test.ts",
 		"./vs/base/test/common/utils.ts",
 		"./vs/base/test/node/processes/fixtures/fork_large.ts",
 		"./vs/base/test/node/processes/fixtures/fork.ts",
@@ -115,6 +118,7 @@
 		"./vs/code/electron-main/keyboard.ts",
 		"./vs/code/electron-main/sharedProcess.ts",
 		"./vs/code/electron-main/theme.ts",
+		"./vs/code/node/paths.ts",
 		"./vs/code/node/shellEnv.ts",
 		"./vs/code/node/wait.ts",
 		"./vs/code/node/windowsFinder.ts",
diff --git a/src/vs/base/common/paths.ts b/src/vs/base/common/paths.ts
index b2b255b0f1b..1255aed38cf 100644
--- a/src/vs/base/common/paths.ts
+++ b/src/vs/base/common/paths.ts
@@ -72,7 +72,10 @@ function _isNormal(path: string, win: boolean): boolean {
 		: !_posixBadPath.test(path);
 }
 
-export function normalize(path: string, toOSPath?: boolean): string {
+export function normalize(path: undefined, toOSPath?: boolean): undefined;
+export function normalize(path: null, toOSPath?: boolean): null;
+export function normalize(path: string, toOSPath?: boolean): string;
+export function normalize(path: string | null | undefined, toOSPath?: boolean): string | null | undefined {
 
 	if (path === null || path === void 0) {
 		return path;
@@ -288,7 +291,7 @@ export function isUNC(path: string): boolean {
 // Reference: https://en.wikipedia.org/wiki/Filename
 const INVALID_FILE_CHARS = isWindows ? /[\\/:\*\?"<>\|]/g : /[\\/]/g;
 const WINDOWS_FORBIDDEN_NAMES = /^(con|prn|aux|clock\$|nul|lpt[0-9]|com[0-9])$/i;
-export function isValidBasename(name: string): boolean {
+export function isValidBasename(name: string | null | undefined): boolean {
 	if (!name || name.length === 0 || /^\s+$/.test(name)) {
 		return false; // require a name that is not just whitespace
 	}
diff --git a/src/vs/base/common/strings.ts b/src/vs/base/common/strings.ts
index 7c6a9820fbe..f9f44b040db 100644
--- a/src/vs/base/common/strings.ts
+++ b/src/vs/base/common/strings.ts
@@ -78,7 +78,7 @@ export function escapeRegExpCharacters(value: string): string {
  * @param haystack string to trim
  * @param needle the thing to trim (default is a blank)
  */
-export function trim(haystack: string, needle: string = ' '): string | undefined {
+export function trim(haystack: string, needle: string = ' '): string {
 	let trimmed = ltrim(haystack, needle);
 	return rtrim(trimmed, needle);
 }
diff --git a/src/vs/code/node/paths.ts b/src/vs/code/node/paths.ts
index 5774c6b6265..f322145cbac 100644
--- a/src/vs/code/node/paths.ts
+++ b/src/vs/code/node/paths.ts
@@ -35,7 +35,7 @@ function doValidatePaths(args: string[], gotoLineMode?: boolean): string[] {
 	const result = args.map(arg => {
 		let pathCandidate = String(arg);
 
-		let parsedPath: IPathWithLineAndColumn;
+		let parsedPath: IPathWithLineAndColumn | undefined = undefined;
 		if (gotoLineMode) {
 			parsedPath = parseLineAndColumnAware(pathCandidate);
 			pathCandidate = parsedPath.path;
@@ -52,7 +52,7 @@ function doValidatePaths(args: string[], gotoLineMode?: boolean): string[] {
 			return null; // do not allow invalid file names
 		}
 
-		if (gotoLineMode) {
+		if (gotoLineMode && parsedPath) {
 			parsedPath.path = sanitizedFilePath;
 
 			return toPath(parsedPath);
@@ -62,7 +62,7 @@ function doValidatePaths(args: string[], gotoLineMode?: boolean): string[] {
 	});
 
 	const caseInsensitive = platform.isWindows || platform.isMacintosh;
-	const distinct = arrays.distinct(result, e => e && caseInsensitive ? e.toLowerCase() : e);
+	const distinct = arrays.distinct(result, e => e && caseInsensitive ? e.toLowerCase() : (e || ''));
 
 	return arrays.coalesce(distinct);
 }
@@ -98,7 +98,7 @@ export interface IPathWithLineAndColumn {
 export function parseLineAndColumnAware(rawPath: string): IPathWithLineAndColumn {
 	const segments = rawPath.split(':'); // C:\file.txt:<line>:<column>
 
-	let path: string;
+	let path: string | null = null;
 	let line: number | null = null;
 	let column: number | null = null;