diff --git a/wagtail/wagtailadmin/blocks.py b/wagtail/wagtailadmin/blocks.py
index 2bd9dffb2..3ef794bb8 100644
--- a/wagtail/wagtailadmin/blocks.py
+++ b/wagtail/wagtailadmin/blocks.py
@@ -6,6 +6,7 @@ from django.utils.html import format_html, format_html_join
 from django.utils.safestring import mark_safe
 from django.utils.text import capfirst
 from django.utils.encoding import python_2_unicode_compatible
+from django.utils.deconstruct import deconstructible
 from django.template.loader import render_to_string
 from django.forms import Media
 from django.forms.utils import ErrorList
@@ -35,6 +36,7 @@ def js_dict(d):
 # Top-level superclasses and helper objects
 # =========================================
 
+@deconstructible
 class Block(object):
     creation_counter = 0
 
@@ -206,6 +208,11 @@ class TextInputBlock(Block):
 # Field block
 # ===========
 
+# FIXME: form field instances are not deconstructible for migrations. Need some other way to refer to
+# them in the initialiser, in the case that FieldBlock appears inline within a StreamField definition.
+# (Referring to them by class would probably work; it's unlikely that any parameter passed to them
+# would affect anything you're doing in migrations)
+
 class FieldBlock(Block):
     default = None
 
diff --git a/wagtail/wagtailcore/fields.py b/wagtail/wagtailcore/fields.py
index e5f7f4d16..a459d6071 100644
--- a/wagtail/wagtailcore/fields.py
+++ b/wagtail/wagtailcore/fields.py
@@ -36,3 +36,14 @@ class RichTextField(models.TextField):
         defaults = {'widget': RichTextArea}
         defaults.update(kwargs)
         return super(RichTextField, self).formfield(**defaults)
+
+
+class StreamField(models.TextField):
+    def __init__(self, block_types, **kwargs):
+        self.block_types = block_types
+        super(StreamField, self).__init__(**kwargs)
+
+    def deconstruct(self):
+        name, path, args, kwargs = super(StreamField, self).deconstruct()
+        kwargs['block_types'] = self.block_types
+        return name, path, args, kwargs