diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 597b323661f..1acb342daa4 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -2869,8 +2869,6 @@ function trimEndImpl(s: string) {
     return s.slice(0, end + 1);
 }
 
-declare const process: any;
-
 /** @internal */
 export function isNodeLikeSystem(): boolean {
     // This is defined here rather than in sys.ts to prevent a cycle from its
@@ -2880,7 +2878,7 @@ export function isNodeLikeSystem(): boolean {
     // when bundled using esbuild, this function will be rewritten to `__require`
     // and definitely exist.
     return typeof process !== "undefined"
-        && process.nextTick
-        && !process.browser
+        && !!process.nextTick
+        && !(process as any).browser
         && typeof module === "object";
 }
diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index 547bcd680a0..45e456454bc 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -1443,12 +1443,6 @@ interface DirectoryWatcher extends FileWatcher {
     referenceCount: number;
 }
 
-declare const require: any;
-declare const process: any;
-declare const global: any;
-declare const __filename: string;
-declare const __dirname: string;
-
 // TODO: GH#18217 this is used as if it's certainly defined in many places.
 export let sys: System = (() => {
     // NodeJS detects "\uFEFF" at the start of the string and *replaces* it with the actual
@@ -1507,7 +1501,7 @@ export let sys: System = (() => {
             getAccessibleSortedChildDirectories: path => getAccessibleFileSystemEntries(path).directories,
             realpath,
             tscWatchFile: process.env.TSC_WATCHFILE,
-            useNonPollingWatchers: process.env.TSC_NONPOLLING_WATCHER,
+            useNonPollingWatchers: !!process.env.TSC_NONPOLLING_WATCHER,
             tscWatchDirectory: process.env.TSC_WATCHDIRECTORY,
             inodeWatching: isLinuxOrMacOs,
             sysLog,
@@ -1584,7 +1578,7 @@ export let sys: System = (() => {
             disableCPUProfiler,
             cpuProfilingEnabled: () => !!activeSession || contains(process.execArgv, "--cpu-prof") || contains(process.execArgv, "--prof"),
             realpath,
-            debugMode: !!process.env.NODE_INSPECTOR_IPC || !!process.env.VSCODE_INSPECTOR_OPTIONS || some(process.execArgv as string[], arg => /^--(inspect|debug)(-brk)?(=\d+)?$/i.test(arg)),
+            debugMode: !!process.env.NODE_INSPECTOR_IPC || !!process.env.VSCODE_INSPECTOR_OPTIONS || some(process.execArgv, arg => /^--(inspect|debug)(-brk)?(=\d+)?$/i.test(arg)),
             tryEnableSourceMapsForHost() {
                 try {
                     (require("source-map-support") as typeof import("source-map-support")).install();
@@ -1599,8 +1593,9 @@ export let sys: System = (() => {
                 process.stdout.write("\x1Bc");
             },
             setBlocking: () => {
-                if (process.stdout && process.stdout._handle && process.stdout._handle.setBlocking) {
-                    process.stdout._handle.setBlocking(true);
+                const handle = (process.stdout as any)?._handle as { setBlocking?: (value: boolean) => void };
+                if (handle && handle.setBlocking) {
+                    handle.setBlocking(true);
                 }
             },
             bufferFrom,
diff --git a/src/harness/evaluatorImpl.ts b/src/harness/evaluatorImpl.ts
index 0f922794560..f72526fb4a1 100644
--- a/src/harness/evaluatorImpl.ts
+++ b/src/harness/evaluatorImpl.ts
@@ -5,8 +5,6 @@ import * as ts from "./_namespaces/ts";
 import * as vfs from "./_namespaces/vfs";
 import * as vpath from "./_namespaces/vpath";
 
-declare let Symbol: SymbolConstructor;
-
 const sourceFile = vpath.combine(vfs.srcFolder, "source.ts");
 const sourceFileJs = vpath.combine(vfs.srcFolder, "source.js");