After checking more combination of (Apache server, Django development server) and (Compress, no compress), it turns out that it happens when offline compression is disabled.
When I specified the below in local_settings.py, it happens both with Apache2 server and Django dev server.
COMPRESS_OFFLINE = False
COMPRESS_ENABLED = False
(Note that I have't tested COMPRESS_ENABLED=True and COMPRESS_OFFLINE=False)
After checking more combination of (Apache server, Django development server) and (Compress, no compress), it turns out that it happens when offline compression is disabled.
When I specified the below in local_settings.py, it happens both with Apache2 server and Django dev server.
COMPRESS_OFFLINE = False
COMPRESS_ENABLED = False
(Note that I have't tested COMPRESS_ ENABLED= True and COMPRESS_ OFFLINE= False)