Save buttons missing in django admin - mysql

Question

I have 2 simple models:
class Doll(models.Model):
name = models.CharField(max_length=32)
doll_type = models.CharField(max_length=16, choices=DOLL_TYPE_CHOICES)
mark = models.CharField(max_length=48, help_text='trademark on the body of the doll', default='')
body = models.CharField(max_length=16, choices = BODY_CHOICES)
factory = models.CharField(max_length=24, choices=FACTORY_CHOICES)
class DollLink(models.Model):
doll = models.ForeignKey(Doll)
link_type = models.CharField(max_length=16, choices=LINK_TYPE_CHOICES)
url = models.URLField(default='')
In admin.py:
class DollLinkInline(admin.TabularInline):
model = DollLink
fields = ('link_type', 'url')
extra = 1
class DollAdmin(admin.ModelAdmin):
list_display = ('name', 'doll_type', 'body', 'factory')
list_filter = ('doll_type', 'body', 'factory')
inlines = (DollLinkInline,)
admin.site.register(Doll, DollAdmin)
If I want to add a new Doll or edit an existing one, then the save buttons are missing. It seems to me that it's related to inlines, cause if I remove the inline, the save buttons are back, and can add/edit Doll and DollLink separately. But if I put back the inline, again no save option. No js error on page.
I used django and inlines previously, and never experienced anything like that, nor found any similar issues with google.
My django version is 1.6.5, use MySQL and Cloud9 IDE.