diff --git a/config/install/geshifilter.settings.yml b/config/install/geshifilter.settings.yml
index ffef5ca..f3d4cd5 100644
--- a/config/install/geshifilter.settings.yml
+++ b/config/install/geshifilter.settings.yml
@@ -44,6 +44,9 @@ tag_styles:
   8: 0
   16: 0
 
+# Tab width, the default from geshi is 8.
+tab_width: 8
+
 # Default languages and tags.
 language:
   php:
diff --git a/config/schema/geshifilter.shema.yml b/config/schema/geshifilter.shema.yml
index d5a3c83..2848aa3 100644
--- a/config/schema/geshifilter.shema.yml
+++ b/config/schema/geshifilter.shema.yml
@@ -33,6 +33,8 @@ geshifilter.settings:
       type: sequence
       sequence:
         - type: integer
+    tab_width:
+      type: integer
     language:
       type: sequence
       sequence:
diff --git a/src/Form/GeshiFilterSettingsForm.php b/src/Form/GeshiFilterSettingsForm.php
index ab332b4..c7d5709 100644
--- a/src/Form/GeshiFilterSettingsForm.php
+++ b/src/Form/GeshiFilterSettingsForm.php
@@ -136,6 +136,15 @@ class GeshiFilterSettingsForm extends ConfigFormBase {
           '@line-numbers' => \Drupal::l($this->t('Line numbers'), Url::fromUri('http://qbnz.com/highlighter/geshi-doc.html#line-numbers')),
         ]),
       ];
+      
+      // Generic tags.
+      $form['highlighting_options']["tab_width"] = [
+        '#type' => 'textfield',
+        '#title' => $this->t('Tab Width'),
+        '#default_value' => $config->get('tab_width'),
+        '#description' => $this->t('How many spaces to use when replacing tabs.'),
+      ];
+      
       // Highlight_string usage option.
       $form['highlighting_options']['use_highlight_string_for_php'] = [
         '#type' => 'checkbox',
@@ -261,6 +270,7 @@ class GeshiFilterSettingsForm extends ConfigFormBase {
       $config->set('use_format_specific_options', $form_state->getValue('use_format_specific_options'))
         ->set('default_highlighting', $form_state->getValue('default_highlighting'))
         ->set('default_line_numbering', $form_state->getValue('default_line_numbering'))
+        ->set('tab_width', $form_state->getValue('tab_width'))
         ->set('use_highlight_string_for_php', $form_state->getValue('use_highlight_string_for_php'))
         ->set('enable_keyword_urls', $form_state->getValue('enable_keyword_urls'))
         ->set('css_mode', $form_state->getValue('css_mode'))
diff --git a/src/GeshiFilterProcess.php b/src/GeshiFilterProcess.php
index b056694..6a0d600 100644
--- a/src/GeshiFilterProcess.php
+++ b/src/GeshiFilterProcess.php
@@ -99,6 +99,8 @@ class GeshiFilterProcess {
     }
     else {
       $geshi->highlight_lines_extra($special_lines);
+      // How many spaces to use for tabs.
+      $geshi->set_tab_width($config->get('tab_width'));
 
       // Block source code mode.
       $geshi->set_header_type((int) $config->get('code_container', GESHI_HEADER_PRE));