diff --git a/ablog/__init__.py b/ablog/__init__.py
index 130ba3a..cc727bc 100755
--- a/ablog/__init__.py
+++ b/ablog/__init__.py
@@ -19,10 +19,20 @@ def anchor(post):
     else:
         return ''
 
+def build_safe(builder):
+    """Return True when builder is expected to be safe. Safe builders are
+    HTML builders, excluding `PickleHTMLBuilder` and `JSONHTMLBuilder`
+    which run into issues when trying to serialize blog objects."""
+
+    if hasattr(builder, 'builder');
+        builder = builder.builder
+
+    return builder.format == 'html' and not builder.name in {'json', 'pickle'}
+
 
 def html_page_context(app, pagename, templatename, context, doctree):
 
-    if app.builder.name in {'html', 'dirhtml'}:
+    if build_safe(app):
         context['ablog'] = Blog(app)
         context['anchor'] = anchor
 
diff --git a/ablog/post.py b/ablog/post.py
index eaa298e..ea5a265 100644
--- a/ablog/post.py
+++ b/ablog/post.py
@@ -18,6 +18,7 @@ from docutils.parsers.rst import directives
 from docutils.utils import relative_path
 
 import ablog
+from . import build_safe
 from .blog import Blog, slugify, os_path_join, revise_pending_xrefs
 
 if sys.version_info >= (3, 0):
@@ -480,7 +481,7 @@ def generate_archive_pages(app):
     """Generate archive pages for all posts, categories, tags, authors, and
     drafts."""
 
-    if app.builder.name not in {'html', 'dirhtml'}:
+    if not build_safe(app):
         return
 
     blog = Blog(app)
@@ -562,7 +563,7 @@ def generate_atom_feeds(app):
     """Generate archive pages for all posts, categories, tags, authors, and
     drafts."""
 
-    if app.builder.name not in {'html', 'dirhtml'}:
+    if not build_safe(app):
         return
 
     blog = Blog(app)