diff --git a/changelog.d/14625.bugfix b/changelog.d/14625.bugfix
new file mode 100644
index 0000000000000000000000000000000000000000..a4d1216690ec118303a44742d658641c1f067d7e
--- /dev/null
+++ b/changelog.d/14625.bugfix
@@ -0,0 +1 @@
+Fix html templates to load images only on HTTPS. Contributed by @ashfame.
diff --git a/synapse/res/templates/_base.html b/synapse/res/templates/_base.html
index 46439fce6aa651b8b5b852495817e56ea7befbca..4b5cc7bcb62a392cfb700ebcde1a6c8af9c270b8 100644
--- a/synapse/res/templates/_base.html
+++ b/synapse/res/templates/_base.html
@@ -13,13 +13,13 @@
<body>
<header class="mx_Header">
{% if app_name == "Riot" %}
- <img src="http://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
+ <img src="https://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
{% elif app_name == "Vector" %}
- <img src="http://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
+ <img src="https://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
{% elif app_name == "Element" %}
<img src="https://static.element.io/images/email-logo.png" width="83" height="83" alt="[Element]"/>
{% else %}
- <img src="http://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
+ <img src="https://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
{% endif %}
</header>
diff --git a/synapse/res/templates/notice_expiry.html b/synapse/res/templates/notice_expiry.html
index 406397aaca768b3853882d01f3799d8cbb5f0737..f62038e111cc8b700f4a96b887cf19cbe14f3682 100644
--- a/synapse/res/templates/notice_expiry.html
+++ b/synapse/res/templates/notice_expiry.html
@@ -21,13 +21,13 @@
</td>
<td class="logo">
{% if app_name == "Riot" %}
- <img src="http://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
+ <img src="https://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
{% elif app_name == "Vector" %}
- <img src="http://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
+ <img src="https://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
{% elif app_name == "Element" %}
<img src="https://static.element.io/images/email-logo.png" width="83" height="83" alt="[Element]"/>
{% else %}
- <img src="http://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
+ <img src="https://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
{% endif %}
</td>
</tr>
diff --git a/synapse/res/templates/notif_mail.html b/synapse/res/templates/notif_mail.html
index 2add9dd859ced891eea5a42af568a05156adb8f8..7da0fff5e946523d57f0dade1b11bccb38756974 100644
--- a/synapse/res/templates/notif_mail.html
+++ b/synapse/res/templates/notif_mail.html
@@ -22,13 +22,13 @@
</td>
<td class="logo">
{%- if app_name == "Riot" %}
- <img src="http://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
+ <img src="https://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
{%- elif app_name == "Vector" %}
- <img src="http://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
+ <img src="https://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
{%- elif app_name == "Element" %}
<img src="https://static.element.io/images/email-logo.png" width="83" height="83" alt="[Element]"/>
{%- else %}
- <img src="http://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
+ <img src="https://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
{%- endif %}
</td>
</tr>