diff --git a/server/src/eslint.ts b/server/src/eslint.ts
index 8baf04dc..7790ef03 100644
--- a/server/src/eslint.ts
+++ b/server/src/eslint.ts
@@ -1170,7 +1170,7 @@ export namespace ESLint {
 		if (result.length === 0) {
 			return result;
 		}
-		return result[result.length - 1] === path.sep
+		return result.endsWith(path.sep)
 			? result.substring(0, result.length - 1)
 			: result;
 	}
@@ -1334,8 +1334,8 @@ export namespace ESLint {
 			if (typeof err.message === 'string' || err.message instanceof String) {
 				result = <string>err.message;
 				result = result.replace(/\r?\n/g, ' ');
-				if (/^CLI: /.test(result)) {
-					result = result.substr(5);
+				if (result.startsWith('CLI: ')) {
+					result = result.slice(5);
 				}
 			} else {
 				result = `An unknown error occurred while validating document: ${document.uri}`;
diff --git a/server/src/eslintServer.ts b/server/src/eslintServer.ts
index d9cd31c9..82c5aec5 100644
--- a/server/src/eslintServer.ts
+++ b/server/src/eslintServer.ts
@@ -802,7 +802,7 @@ async function computeAllFixes(identifier: VersionedTextDocumentIdentifier, mode
 							start: textDocument.positionAt(diff.originalStart),
 							end: textDocument.positionAt(diff.originalStart + diff.originalLength)
 						},
-						newText: fixedContent.substr(diff.modifiedStart, diff.modifiedLength)
+						newText: fixedContent.slice(diff.modifiedStart, diff.modifiedStart + diff.modifiedLength)
 					});
 				}
 			}