diff --git a/frontend/index.html b/frontend/index.html
index 99f6f93..742faf2 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -17,7 +17,7 @@
     <button id="update" class="btn btn-primary m-1 float-right">Get data</button>
     <p id="debug">
     </p>
-    <canvas id="spectrogram" width="480" height="480" class="m-3"></canvas>
+    <canvas id="spectrogram" width="480px" height="480px"></canvas>
     <table class="table table-sm">
       <thead class="thead-dark">
         <tr>