diff --git a/build-system/pr-check/build-targets.js b/build-system/pr-check/build-targets.js
index ee2d3f297e4e..88c2c6614ac6 100644
--- a/build-system/pr-check/build-targets.js
+++ b/build-system/pr-check/build-targets.js
@@ -189,8 +189,7 @@ const targetMatchers = {
     }
     return (
       file.startsWith('validator/java/') ||
-      file === 'build-system/tasks/validator.js' ||
-      isValidatorFile(file)
+      file === 'build-system/tasks/validator.js'
     );
   },
   'VALIDATOR_WEBUI': (file) => {
diff --git a/build-system/pr-check/build.js b/build-system/pr-check/build.js
index 68fbfeb8da5d..d92cecddd7f7 100644
--- a/build-system/pr-check/build.js
+++ b/build-system/pr-check/build.js
@@ -36,8 +36,7 @@ const {runYarnChecks} = require('./yarn-checks');
 
 const FILENAME = 'build.js';
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 function main() {
   const startTime = startTimer(FILENAME, FILENAME);
diff --git a/build-system/pr-check/checks.js b/build-system/pr-check/checks.js
index c1402e4ab2f5..4f340a7e2b70 100644
--- a/build-system/pr-check/checks.js
+++ b/build-system/pr-check/checks.js
@@ -35,8 +35,7 @@ const {reportAllExpectedTests} = require('../tasks/report-test-status');
 const {runYarnChecks} = require('./yarn-checks');
 
 const FILENAME = 'checks.js';
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 async function main() {
   const startTime = startTimer(FILENAME, FILENAME);
diff --git a/build-system/pr-check/dist-bundle-size.js b/build-system/pr-check/dist-bundle-size.js
index 0ac16e70c1a3..a0d95a462b39 100644
--- a/build-system/pr-check/dist-bundle-size.js
+++ b/build-system/pr-check/dist-bundle-size.js
@@ -39,8 +39,7 @@ const {signalDistUpload} = require('../tasks/pr-deploy-bot-utils');
 
 const FILENAME = 'dist-bundle-size.js';
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 async function main() {
   const startTime = startTimer(FILENAME, FILENAME);
diff --git a/build-system/pr-check/e2e-tests.js b/build-system/pr-check/e2e-tests.js
index 2a34e09082b3..62f37da13196 100644
--- a/build-system/pr-check/e2e-tests.js
+++ b/build-system/pr-check/e2e-tests.js
@@ -34,8 +34,7 @@ const {isTravisPullRequestBuild} = require('../common/travis');
 
 const FILENAME = 'e2e-tests.js';
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 async function main() {
   const startTime = startTimer(FILENAME, FILENAME);
diff --git a/build-system/pr-check/experiment-tests.js b/build-system/pr-check/experiment-tests.js
index ca131266ae89..d062dac351f4 100644
--- a/build-system/pr-check/experiment-tests.js
+++ b/build-system/pr-check/experiment-tests.js
@@ -31,8 +31,7 @@ const {
 const {experiment} = require('minimist')(process.argv.slice(2));
 const FILENAME = `${experiment}-tests.js`;
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 function getConfig_() {
   const config = experimentsConfig[experiment];
diff --git a/build-system/pr-check/local-tests.js b/build-system/pr-check/local-tests.js
index af1ef682cd9e..91d20f92e6b6 100644
--- a/build-system/pr-check/local-tests.js
+++ b/build-system/pr-check/local-tests.js
@@ -34,8 +34,7 @@ const {isTravisPullRequestBuild} = require('../common/travis');
 
 const FILENAME = 'local-tests.js';
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 function main() {
   const startTime = startTimer(FILENAME, FILENAME);
diff --git a/build-system/pr-check/module-dist-bundle-size.js b/build-system/pr-check/module-dist-bundle-size.js
index b689b8aff0f1..4cafe63ea085 100644
--- a/build-system/pr-check/module-dist-bundle-size.js
+++ b/build-system/pr-check/module-dist-bundle-size.js
@@ -36,8 +36,7 @@ const {runYarnChecks} = require('./yarn-checks');
 
 const FILENAME = 'module-dist-bundle-size.js';
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 function main() {
   const startTime = startTimer(FILENAME, FILENAME);
diff --git a/build-system/pr-check/single-pass-tests.js b/build-system/pr-check/single-pass-tests.js
index 6c144799936a..25abcdcdc9f6 100644
--- a/build-system/pr-check/single-pass-tests.js
+++ b/build-system/pr-check/single-pass-tests.js
@@ -33,8 +33,7 @@ const {isTravisPullRequestBuild} = require('../common/travis');
 
 const FILENAME = 'single-pass-tests.js';
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 function main() {
   const startTime = startTimer(FILENAME, FILENAME);
diff --git a/build-system/pr-check/validator-tests.js b/build-system/pr-check/validator-tests.js
index 36cbf448d8a1..49e3e6fda095 100644
--- a/build-system/pr-check/validator-tests.js
+++ b/build-system/pr-check/validator-tests.js
@@ -27,6 +27,7 @@ const {
   startTimer,
   stopTimer,
   stopTimedJob,
+  timedExec: timedExecBase,
   timedExecOrDie: timedExecOrDieBase,
 } = require('./utils');
 const {determineBuildTargets} = require('./build-targets');
@@ -35,8 +36,8 @@ const {runYarnChecks} = require('./yarn-checks');
 
 const FILENAME = 'validator-tests.js';
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
+const timedExec = (cmd) => timedExecBase(cmd, FILENAME);
 
 function main() {
   const startTime = startTimer(FILENAME, FILENAME);
@@ -47,7 +48,8 @@ function main() {
 
   if (!isTravisPullRequestBuild()) {
     timedExecOrDie('gulp validator');
-    timedExecOrDie('gulp validator-java');
+    // #27786: Java validator is not guaranteed to be in sync with AMP code.
+    timedExec('gulp validator-java');
     timedExecOrDie('gulp validator-webui');
   } else {
     printChangeSummary(FILENAME);
@@ -72,8 +74,10 @@ function main() {
       timedExecOrDie('gulp validator');
     }
 
-    if (buildTargets.has('RUNTIME') || buildTargets.has('VALIDATOR_JAVA')) {
+    if (buildTargets.has('VALIDATOR_JAVA')) {
       timedExecOrDie('gulp validator-java');
+    } else if (buildTargets.has('RUNTIME')) {
+      timedExec('gulp validator-java');
     }
 
     if (buildTargets.has('VALIDATOR_WEBUI')) {
diff --git a/build-system/pr-check/visual-diff-tests.js b/build-system/pr-check/visual-diff-tests.js
index c167193b7eb1..c801393793c3 100644
--- a/build-system/pr-check/visual-diff-tests.js
+++ b/build-system/pr-check/visual-diff-tests.js
@@ -35,8 +35,7 @@ const {isTravisPullRequestBuild} = require('../common/travis');
 
 const FILENAME = 'visual-diff-tests.js';
 const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
-const timedExecOrDie = (cmd, unusedFileName) =>
-  timedExecOrDieBase(cmd, FILENAME);
+const timedExecOrDie = (cmd) => timedExecOrDieBase(cmd, FILENAME);
 
 function main() {
   const startTime = startTimer(FILENAME, FILENAME);
diff --git a/build-system/tasks/pr-check.js b/build-system/tasks/pr-check.js
index 9d22627d58a7..55789f0dfac5 100644
--- a/build-system/tasks/pr-check.js
+++ b/build-system/tasks/pr-check.js
@@ -114,6 +114,10 @@ async function prCheck(cb) {
     runCheck('gulp validator');
   }
 
+  if (buildTargets.has('VALIDATOR_JAVA')) {
+    runCheck('gulp validator-java');
+  }
+
   if (buildTargets.has('VALIDATOR_WEBUI')) {
     runCheck('gulp validator-webui');
   }