diff --git a/includes/resourceloader/ResourceLoaderStartUpModule.php b/includes/resourceloader/ResourceLoaderStartUpModule.php
index 16154ad7dae..e3447360521 100644
--- a/includes/resourceloader/ResourceLoaderStartUpModule.php
+++ b/includes/resourceloader/ResourceLoaderStartUpModule.php
@@ -114,7 +114,6 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 			'wgCookieDomain' => $conf->get( 'CookieDomain' ),
 			'wgCookiePath' => $conf->get( 'CookiePath' ),
 			'wgCookieExpiration' => $conf->get( 'CookieExpiration' ),
-			'wgResourceLoaderMaxQueryLength' => $conf->get( 'ResourceLoaderMaxQueryLength' ),
 			'wgCaseSensitiveNamespaces' => $caseSensitiveNamespaces,
 			'wgLegalTitleChars' => Title::convertByteClassToUnicodeClass( Title::legalChars() ),
 			'wgIllegalFileChars' => Title::convertByteClassToUnicodeClass( $illegalFileChars ),
@@ -409,6 +408,9 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 		// Perform replacements for mediawiki.js
 		$mwLoaderPairs = [
 			'$VARS.baseModules' => ResourceLoader::encodeJsonForScript( $this->getBaseModules() ),
+			'$VARS.maxQueryLength' => ResourceLoader::encodeJsonForScript(
+				$conf->get( 'ResourceLoaderMaxQueryLength' )
+			),
 		];
 		$profilerStubs = [
 			'$CODE.profileExecuteStart();' => 'mw.loader.profiler.onExecuteStart( module );',
diff --git a/maintenance/jsduck/eg-iframe.html b/maintenance/jsduck/eg-iframe.html
index 3b83ea67fb2..c1354e36ce7 100644
--- a/maintenance/jsduck/eg-iframe.html
+++ b/maintenance/jsduck/eg-iframe.html
@@ -34,10 +34,12 @@
 		};
 	</script>
 	<script>
-		// Mock startup.js
+		// Mock ResourceLoaderStartUpModule substitutions
 		window.$VARS = {
-			baseModules: []
+			baseModules: [],
+			maxQueryLength: 2000
 		};
+		// Mock startup.js
 		window.RLQ = [];
 	</script>
 	<script src="modules/src/startup/mediawiki.js"></script>
diff --git a/resources/src/startup/mediawiki.js b/resources/src/startup/mediawiki.js
index c08d259ac69..28f57dbd8dc 100644
--- a/resources/src/startup/mediawiki.js
+++ b/resources/src/startup/mediawiki.js
@@ -1579,7 +1579,7 @@
 			 * @param {string[]} batch
 			 */
 			function batchRequest( batch ) {
-				var reqBase, splits, maxQueryLength, b, bSource, bGroup,
+				var reqBase, splits, b, bSource, bGroup,
 					source, group, i, modules, sourceLoadScript,
 					currReqBase, currReqBaseLength, moduleMap, currReqModules, l,
 					lastDotIndex, prefix, suffix, bytesAdded;
@@ -1618,7 +1618,6 @@
 					lang: mw.config.get( 'wgUserLanguage' ),
 					debug: mw.config.get( 'debug' )
 				};
-				maxQueryLength = mw.config.get( 'wgResourceLoaderMaxQueryLength', 2000 );
 
 				// Split module list by source and by group.
 				splits = Object.create( null );
@@ -1674,7 +1673,7 @@
 								modules[ i ].length + 3; // '%7C'.length == 3
 
 							// If the url would become too long, create a new one, but don't create empty requests
-							if ( maxQueryLength > 0 && currReqModules.length && l + bytesAdded > maxQueryLength ) {
+							if ( currReqModules.length && l + bytesAdded > mw.loader.maxQueryLength ) {
 								// Dispatch what we've got...
 								doRequest();
 								// .. and start again.
@@ -1682,7 +1681,7 @@
 								moduleMap = Object.create( null );
 								currReqModules = [];
 
-								mw.track( 'resourceloader.splitRequest', { maxQueryLength: maxQueryLength } );
+								mw.track( 'resourceloader.splitRequest', { maxQueryLength: mw.loader.maxQueryLength } );
 							}
 							if ( !moduleMap[ prefix ] ) {
 								moduleMap[ prefix ] = [];
@@ -1792,6 +1791,15 @@
 				 */
 				moduleRegistry: registry,
 
+				/**
+				 * Exposed for testing and debugging only.
+				 *
+				 * @see #batchRequest
+				 * @property
+				 * @private
+				 */
+				maxQueryLength: $VARS.maxQueryLength,
+
 				/**
 				 * @inheritdoc #newStyleTag
 				 * @method
diff --git a/tests/qunit/suites/resources/mediawiki/mediawiki.loader.test.js b/tests/qunit/suites/resources/mediawiki/mediawiki.loader.test.js
index 8b06bd6e1fb..e17c78d7af4 100644
--- a/tests/qunit/suites/resources/mediawiki/mediawiki.loader.test.js
+++ b/tests/qunit/suites/resources/mediawiki/mediawiki.loader.test.js
@@ -15,6 +15,7 @@
 			};
 		},
 		teardown: function () {
+			mw.loader.maxQueryLength = 2000;
 			// Teardown for StringSet shim test
 			if ( this.nativeSet ) {
 				window.Set = this.nativeSet;
@@ -624,7 +625,7 @@
 			[ 'testUrlIncDump', 'dump', [], null, 'testloader' ]
 		] );
 
-		mw.config.set( 'wgResourceLoaderMaxQueryLength', 10 );
+		mw.loader.maxQueryLength = 10;
 
 		return mw.loader.using( [ 'testUrlIncDump', 'testUrlInc' ] ).then( function ( require ) {
 			assert.propEqual(