diff --git a/includes/CitizenHooks.php b/includes/CitizenHooks.php
index ced426f0..66644a36 100644
--- a/includes/CitizenHooks.php
+++ b/includes/CitizenHooks.php
@@ -88,6 +88,15 @@ class CitizenHooks {
 	 * @return bool
 	 */
 	public static function onThumbnailBeforeProduceHTML( $thumb, &$attribs, &$linkAttribs ) {
+		try {
+			$config = MediaWikiServices::getInstance()->getConfigFactory()->makeConfig( 'Citizen' );
+			$thumbSize = $config->get( 'ThumbnailSize' );
+		} catch ( ConfigException $e ) {
+			wfLogWarning( sprintf( 'Could not get config for "$wgThumbnailSize". Defaulting to "10". %s',
+				$e->getMessage() ) );
+			$thumbSize = 10;
+		}
+
 		$file = $thumb->getFile();
 
 		if ( $file !== null ) {
@@ -112,7 +121,8 @@ class CitizenHooks {
 			$attribs['data-height'] = $attribs['height'];
 
 			// Replace src with small size image
-			$attribs['src'] = preg_replace( '#/\d+px-#', '/10px-', $attribs['src'] );
+			$attribs['src'] =
+				preg_replace( '#/\d+px-#', sprintf( '/%upx-', $thumbSize ), $attribs['src'] );
 
 			// So that the 10px thumbnail is enlarged to the right size
 			$attribs['width'] = $attribs['data-width'];
diff --git a/skin.json b/skin.json
index 45a89e78..0630deb5 100644
--- a/skin.json
+++ b/skin.json
@@ -164,6 +164,12 @@
 			"description": "Page tools visibility condition",
 			"descriptionmsg": "citizen-config-showpagetools",
 			"public": true
+		},
+		"ThumbnailSize": {
+			"value": 10,
+			"description": "Thumbnail size to use for lazy-loading",
+			"descriptionmsg": "citizen-config-thumbnailsize",
+			"public": true
 		}
 	},
 	"ConfigRegistry": {