diff --git a/ext/bg/js/options-form.js b/ext/bg/js/options-form.js
index 712b7243..c72508c6 100644
--- a/ext/bg/js/options-form.js
+++ b/ext/bg/js/options-form.js
@@ -49,6 +49,7 @@ function formToOptions(section, callback) {
                 break;
             case 'anki':
                 optsNew.ankiCardTags    = $('#anki-card-tags').val().split(/[,; ]+/);
+                optsNew.sentenceExtent  = parseInt($('#sentence-extent').val());
                 optsNew.ankiVocabDeck   = $('#anki-vocab-deck').val();
                 optsNew.ankiVocabModel  = $('#anki-vocab-model').val();
                 optsNew.ankiVocabFields = fieldsToDict($('#vocab .anki-field-value'));
@@ -174,6 +175,7 @@ $(document).ready(() => {
         $('#enable-anki-connect').prop('checked', opts.enableAnkiConnect);
 
         $('#anki-card-tags').val(opts.ankiCardTags.join(' '));
+        $('#sentence-extent').val(opts.sentenceExtent);
 
         $('.options-general input').change(onOptionsGeneralChanged);
         $('.options-anki input').change(onOptionsAnkiChanged);
diff --git a/ext/bg/js/options.js b/ext/bg/js/options.js
index 18707e43..44236e68 100644
--- a/ext/bg/js/options.js
+++ b/ext/bg/js/options.js
@@ -26,6 +26,7 @@ function sanitizeOptions(options) {
         enableAudioPlayback: true,
         enableAnkiConnect:   false,
         ankiCardTags:        ['yomichan'],
+        sentenceExtent:      200,
         ankiVocabDeck:       '',
         ankiVocabModel:      '',
         ankiVocabFields:     {},
diff --git a/ext/bg/options.html b/ext/bg/options.html
index 17f6874d..7e03ea15 100644
--- a/ext/bg/options.html
+++ b/ext/bg/options.html
@@ -12,9 +12,9 @@
 
             .tab-content {
                 border-bottom: 1px #ddd solid;
-                border-left:   1px #ddd solid;
-                border-right:  1px #ddd solid;
-                padding:       10px;
+                border-left: 1px #ddd solid;
+                border-right: 1px #ddd solid;
+                padding: 10px;
             }
 
             .error-dlg {
@@ -92,6 +92,11 @@
                         <div class="col-sm-10"><input type="text" id="anki-card-tags" class="form-control"></div>
                     </div>
 
+                    <div class="form-group">
+                        <label for="sentence-extent" class="control-label col-sm-2">Sentence extent</label>
+                        <div class="col-sm-10"><input type="number" min="1" id="sentence-extent" class="form-control"></div>
+                    </div>
+
                     <ul class="nav nav-tabs col-sm-offset-2 col-sm-10">
                         <li class="active"><a href="#vocab" data-toggle="tab">Vocabulary</a></li>
                         <li><a href="#kanji" data-toggle="tab">Kanji</a></li>
diff --git a/ext/fg/js/client.js b/ext/fg/js/client.js
index a8fbaa68..e59718d6 100644
--- a/ext/fg/js/client.js
+++ b/ext/fg/js/client.js
@@ -25,7 +25,6 @@ class Client {
         this.lastTextSource = null;
         this.activateKey = 16;
         this.activateBtn = 2;
-        this.sentenceExtent = 200;
         this.enabled = false;
         this.options = {};
         this.definitions = null;
@@ -97,7 +96,7 @@ class Client {
             } else {
                 textSource.setEndOffset(length);
 
-                const sentence = Client.extractSentence(textSource, this.sentenceExtent);
+                const sentence = Client.extractSentence(textSource, this.opts.sentenceExtent);
                 definitions.forEach((definition) => {
                     definition.url = window.location.href;
                     definition.sentence = sentence;