diff --git a/IPython/nbconvert/templates/html/basic.tpl b/IPython/nbconvert/templates/html/basic.tpl
index 9b8b76f..d1947db 100644
--- a/IPython/nbconvert/templates/html/basic.tpl
+++ b/IPython/nbconvert/templates/html/basic.tpl
@@ -59,6 +59,7 @@ In [{{ cell.prompt_number }}]:
 {% endblock output %}
 
 {% block markdowncell scoped %}
+<div class="cell border-box-sizing text_cell">
 <div class="input">
 {{ self.empty_in_prompt() }}
 <div class="inner_cell">
@@ -67,9 +68,11 @@ In&nbsp;[{{ cell.prompt_number }}]:
 </div>
 </div>
 </div>
+</div>
 {%- endblock markdowncell %}
 
 {% block headingcell scoped %}
+<div class="cell border-box-sizing text_cell">
 <div class="input">
 {{ self.empty_in_prompt() }}
 <div class="inner_cell">
@@ -78,6 +81,7 @@ In&nbsp;[{{ cell.prompt_number }}]:
 </div>
 </div>
 </div>
+</div>
 {% endblock headingcell %}
 
 {% block unknowncell scoped %}