diff --git a/tfjs-core/src/backends/backend.ts b/tfjs-core/src/backends/backend.ts
index fd3dbbaab3d..aeb9ab3897a 100644
--- a/tfjs-core/src/backends/backend.ts
+++ b/tfjs-core/src/backends/backend.ts
@@ -25,7 +25,7 @@ export const EPSILON_FLOAT16 = 1e-4;
 
 // Required information for all backends.
 export interface BackendTimingInfo {
-  kernelMs: number;
+  kernelMs: number|{error: string};
   getExtraProfileInfo?(): string;  // a field for additional timing information
                                    // e.g. packing / unpacking for WebGL backend
 }
diff --git a/tfjs-core/src/backends/webgl/backend_webgl.ts b/tfjs-core/src/backends/webgl/backend_webgl.ts
index 2bce838b3aa..afa45013a53 100644
--- a/tfjs-core/src/backends/webgl/backend_webgl.ts
+++ b/tfjs-core/src/backends/webgl/backend_webgl.ts
@@ -520,18 +520,27 @@ export class MathBackendWebGL extends KernelBackend {
       this.programTimersStack = null;
     }
 
-    const kernelMs = await Promise.all(flattenedActiveTimerQueries);
-
     const res: WebGLTimingInfo = {
       uploadWaitMs: this.uploadWaitMs,
       downloadWaitMs: this.downloadWaitMs,
-      kernelMs: util.sum(kernelMs),
-      getExtraProfileInfo: () =>
-          kernelMs.map((d, i) => ({name: flattenedActiveTimerNames[i], ms: d}))
-              .map(d => `${d.name}: ${d.ms}`)
-              .join(', '),
+      kernelMs: null,
       wallMs: null  // will be filled by the engine
     };
+
+    if (env().getNumber('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE') > 0) {
+      const kernelMs = await Promise.all(flattenedActiveTimerQueries);
+
+      res['kernelMs'] = util.sum(kernelMs);
+      res['getExtraProfileInfo'] = () =>
+          kernelMs.map((d, i) => ({name: flattenedActiveTimerNames[i], ms: d}))
+              .map(d => `${d.name}: ${d.ms}`)
+              .join(', ');
+    } else {
+      res['kernelMs'] = {
+        error: 'WebGL query timers are not supported in this environment.'
+      };
+    }
+
     this.uploadWaitMs = 0;
     this.downloadWaitMs = 0;
     return res;
@@ -542,14 +551,14 @@ export class MathBackendWebGL extends KernelBackend {
   }
 
   private startTimer(): WebGLQuery|CPUTimerQuery {
-    if (env().getNumber('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_VERSION') > 0) {
+    if (env().getNumber('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE') > 0) {
       return this.gpgpu.beginQuery();
     }
     return {startMs: util.now(), endMs: null};
   }
 
   private endTimer(query: WebGLQuery|CPUTimerQuery): WebGLQuery|CPUTimerQuery {
-    if (env().getNumber('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_VERSION') > 0) {
+    if (env().getNumber('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE') > 0) {
       this.gpgpu.endQuery();
       return query;
     }
@@ -558,7 +567,7 @@ export class MathBackendWebGL extends KernelBackend {
   }
 
   private async getQueryTime(query: WebGLQuery|CPUTimerQuery): Promise<number> {
-    if (env().getNumber('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_VERSION') > 0) {
+    if (env().getNumber('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE') > 0) {
       return this.gpgpu.waitForQueryAndGetTime(query as WebGLQuery);
     }
     const timerQuery = query as CPUTimerQuery;
diff --git a/tfjs-core/src/globals.ts b/tfjs-core/src/globals.ts
index 1e6f7122c7d..dd44d50a336 100644
--- a/tfjs-core/src/globals.ts
+++ b/tfjs-core/src/globals.ts
@@ -239,7 +239,9 @@ export function keep<T extends Tensor>(result: T): T {
  * The result is an object with the following properties:
  *
  * - `wallMs`: Wall execution time.
- * - `kernelMs`: Kernel execution time, ignoring data transfer.
+ * - `kernelMs`: Kernel execution time, ignoring data transfer. If using the
+ * WebGL backend and the query timer extension is not available, this will
+ * return an error object.
  * - On `WebGL` The following additional properties exist:
  *   - `uploadWaitMs`: CPU blocking time on texture uploads.
  *   - `downloadWaitMs`: CPU blocking time on texture downloads (readPixels).
diff --git a/tfjs-core/src/profiler.ts b/tfjs-core/src/profiler.ts
index 156336e97ee..e837459d754 100644
--- a/tfjs-core/src/profiler.ts
+++ b/tfjs-core/src/profiler.ts
@@ -77,9 +77,11 @@ export function checkComputationForErrors<D extends DataType>(
 
 export class Logger {
   logKernelProfile(
-      name: string, result: Tensor, vals: TypedArray, timeMs: number,
-      inputs: NamedTensorMap, extraInfo?: string) {
-    const time = util.rightPad(`${timeMs}ms`, 9);
+      name: string, result: Tensor, vals: TypedArray,
+      timeMs: number|{error: string}, inputs: NamedTensorMap,
+      extraInfo?: string) {
+    const time = typeof timeMs === 'number' ? util.rightPad(`${timeMs}ms`, 9) :
+                                              timeMs['error'];
     const paddedName = util.rightPad(name, 25);
     const rank = result.rank;
     const size = result.size;
diff --git a/tfjs-core/src/profiler_test.ts b/tfjs-core/src/profiler_test.ts
index dddae0d0664..0f73753ff87 100644
--- a/tfjs-core/src/profiler_test.ts
+++ b/tfjs-core/src/profiler_test.ts
@@ -16,6 +16,7 @@
  */
 
 import {BackendTimer, BackendTimingInfo} from './backends/backend';
+import {WEBGL_ENVS} from './backends/webgl/backend_webgl_test_registry';
 import * as tf from './index';
 import {describeWithFlags, SYNC_BACKEND_ENVS} from './jasmine_util';
 import {checkComputationForErrors, Logger, Profiler} from './profiler';
@@ -130,6 +131,34 @@ describeWithFlags('profiler.Profiler', SYNC_BACKEND_ENVS, () => {
   });
 });
 
+describeWithFlags('profiling WebGL', WEBGL_ENVS, () => {
+  it('If query timer extension is unavailable, profiler ' +
+         'reports an error for kernelMs.',
+     doneFn => {
+       const savedQueryReliableValue =
+           tf.env().get('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE');
+       tf.env().set('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE', false);
+
+       const logger = new TestLogger();
+       const profiler = new Profiler(tf.backend(), logger);
+
+       spyOn(logger, 'logKernelProfile').and.callThrough();
+       const logKernelProfileSpy = logger.logKernelProfile as jasmine.Spy;
+
+       profiler.profileKernel(
+           'MatMul', {'x': tf.tensor1d([1])}, () => [tf.scalar(1)]);
+
+       setTimeout(() => {
+         expect(logKernelProfileSpy.calls.first().args[3]['error'])
+             .toBeDefined();
+         tf.env().set(
+             'WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE',
+             savedQueryReliableValue);
+         doneFn();
+       }, 0);
+     });
+});
+
 describe('profiler.checkComputationForErrors', () => {
   beforeAll(() => {
     // Silence warnings.