diff --git a/plugins/calendar/skins/elastic/templates/eventedit.html b/plugins/calendar/skins/elastic/templates/eventedit.html
index f7d433f1..5c89ce42 100644
--- a/plugins/calendar/skins/elastic/templates/eventedit.html
+++ b/plugins/calendar/skins/elastic/templates/eventedit.html
@@ -141,7 +141,7 @@
 				<h3 id="aria-label-attachmentuploadform" class="voice"><roundcube:label name="arialabelattachmentuploadform" /></h3>
 				<div id="edit-attachments-form" class="upload-form" role="region" aria-labelledby="aria-label-attachmentuploadform">
 					<roundcube:object name="plugin.attachments_form" mode="hint" />
-					<button class="btn btn-secondary attach" href="#" onclick="rcmail.upload_input('event-attachment-form'); return false"><roundcube:label name="addattachment" /></button>
+					<button type="button" class="btn btn-secondary attach" href="#" onclick="rcmail.upload_input('event-attachment-form'); return false"><roundcube:label name="addattachment" /></button>
 				</div>
 				<div id="edit-attachments">
 					<roundcube:object name="plugin.attachments_list" id="attachmentlist" class="attachmentslist" />
diff --git a/plugins/tasklist/skins/elastic/templates/taskedit.html b/plugins/tasklist/skins/elastic/templates/taskedit.html
index a2cc9275..9ba8531e 100644
--- a/plugins/tasklist/skins/elastic/templates/taskedit.html
+++ b/plugins/tasklist/skins/elastic/templates/taskedit.html
@@ -113,7 +113,7 @@
 				<h3 id="aria-label-attachmentuploadform" class="voice"><roundcube:label name="arialabelattachmentuploadform" /></h3>
 				<div id="taskedit-attachments-form" class="upload-form" role="region" aria-labelledby="aria-label-attachmentuploadform">
 					<roundcube:object name="plugin.attachments_form" mode="hint" />
-					<button class="btn btn-secondary attach" href="#" onclick="rcmail.upload_input('taskedit-attachment-form'); return false"><roundcube:label name="addattachment" /></button>
+					<button type="button" class="btn btn-secondary attach" href="#" onclick="rcmail.upload_input('taskedit-attachment-form'); return false"><roundcube:label name="addattachment" /></button>
 				</div>
 				<div id="taskedit-attachments">
 					<roundcube:object name="plugin.attachments_list" id="taskedit-attachment-list" class="attachmentslist" />