Cached Images Not Loading in HTTPS – Troubleshooting Guide

In my custom theme, I'm loading products images using this :

 <img src="<?php echo $this->helper('catalog/image')->init($_product, 'small_image')->resize(182) ?>" width="182" height="182" alt="<?php echo $this->htmlEscape($_product->getName()) ?>" />

Unfortunatly, theses images are the only medias that are not loaded in https while the website is accessed in https. I double checked configuration.

Example of the resulting url :

http://mydomain.com/media/catalog/product/cache/1/small_image/182x/9df78eab33525d08d6e5fb8d27136e95/n/o/non_deco_mix_plus_1_candle_best.jpg

Note : I've also tried to flush the cache, no clue.

Is there anything else I should do or verify about that?