Textures on custom shaders not updating when modified at runtime

Steps to reproduce:

• Add object to the scene using a custom shader with a texture
• Add abject to the scene using internal shader
• Use the same texture file on both objects
• Leave the editor running and open the texture in an external editor like gimp or photoshop
• Edit the texture and save it

Observed behaviour:

• Texture on custom shader stays the same (not updated)
• Texture on internal shader gets updated

Expected behaviour:

• Texture on both shaders get updated

Work around:

• Restarting the editor will update the texture on the custom shader