diff --git a/app/controllers/api_controller.rb b/app/controllers/api_controller.rb
index 24ea265..11445a0 100644
--- a/app/controllers/api_controller.rb
+++ b/app/controllers/api_controller.rb
@@ -23,6 +23,8 @@ class ApiController < ApplicationController
     preview = RegexpPreview.processor(params[:parse_type]).new(params[:file], params[:parse_type], plugin_config)
 
     render json: preview.matches
+  rescue Fluent::ConfigError => ex
+    render json: { error: "#{ex.class}: #{ex.message}" }
   end
 
   def grok_to_regexp
diff --git a/app/javascript/packs/in_tail_parse.js b/app/javascript/packs/in_tail_parse.js
index 60124bd..9cf205a 100644
--- a/app/javascript/packs/in_tail_parse.js
+++ b/app/javascript/packs/in_tail_parse.js
@@ -139,7 +139,12 @@ $(document).ready(() => {
           }
         }).then(
           (result) => {
-            this.updateHighlightedLines(result.matches)
+            if (result.matches) {
+              this.updateHighlightedLines(result.matches)
+            } else {
+              console.error(result.error)
+              this.previewError = result.error
+            }
           },
           (error) => {
             this.highlightedLines = null