diff --git a/.changelog/46.fixed b/.changelog/46.fixed
new file mode 100644
index 00000000000..a6f35985c71
--- /dev/null
+++ b/.changelog/46.fixed
@@ -0,0 +1,4 @@
+Fix the Sphinx docs build: force the pure-Python protobuf implementation in
+`docs/conf.py` so the zipkin-proto-http exporter can be documented, and add
+`opentelemetry-exporter-opencensus` to the docs requirements (widening its
+`protobuf` constraint to allow protobuf 5) so its API reference renders
diff --git a/docs-requirements.txt b/docs-requirements.txt
index 4cbce8432ed..53af1b8dd1c 100644
--- a/docs-requirements.txt
+++ b/docs-requirements.txt
@@ -13,6 +13,7 @@ sphinx-jekyll-builder==0.3.0
 ./opentelemetry-proto-json
 ./shim/opentelemetry-opencensus-shim
 ./shim/opentelemetry-opentracing-shim
+./exporter/opentelemetry-exporter-opencensus
 ./exporter/opentelemetry-exporter-otlp-proto-common
 ./exporter/opentelemetry-exporter-otlp-proto-http
 ./exporter/opentelemetry-exporter-otlp-proto-grpc
diff --git a/docs/conf.py b/docs/conf.py
index 01b386beacc..e2e5c8a6006 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -18,6 +18,14 @@
 from os import listdir
 from os.path import isdir, join
 
+# The zipkin-proto-http exporter pins protobuf ~= 3.12, but the docs build
+# installs a modern protobuf (see docs-requirements.txt). Generated *_pb2.py
+# modules built against the old runtime raise "Descriptors cannot be created
+# directly" when imported under the C++ implementation of the newer runtime,
+# which makes autodoc silently skip the module. Forcing the pure-Python
+# protobuf implementation avoids that error so the module can be documented.
+os.environ.setdefault("PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION", "python")
+
 # configure django to avoid the following exception:
 # django.core.exceptions.ImproperlyConfigured: Requested settings, but settings
 # are not configured. You must either define the environment variable
diff --git a/docs/exporter/opencensus/opencensus.rst b/docs/exporter/opencensus/opencensus.rst
index 6bdcd6a873c..e34fc1633fc 100644
--- a/docs/exporter/opencensus/opencensus.rst
+++ b/docs/exporter/opencensus/opencensus.rst
@@ -5,3 +5,8 @@ OpenCensus Exporter
     :members:
     :undoc-members:
     :show-inheritance:
+
+.. automodule:: opentelemetry.exporter.opencensus.trace_exporter
+    :members:
+    :undoc-members:
+    :show-inheritance:
diff --git a/exporter/opentelemetry-exporter-opencensus/pyproject.toml b/exporter/opentelemetry-exporter-opencensus/pyproject.toml
index 86dc7ee07e7..98afc3e1370 100644
--- a/exporter/opentelemetry-exporter-opencensus/pyproject.toml
+++ b/exporter/opentelemetry-exporter-opencensus/pyproject.toml
@@ -33,7 +33,7 @@ dependencies = [
   "opencensus-proto >= 0.1.0, < 1.0.0",
   "opentelemetry-api >= 1.45.0.dev",
   "opentelemetry-sdk >= 1.15",
-  "protobuf ~= 3.13",
+  "protobuf >= 3.13, < 8.0",
   "setuptools >= 16.0",
 ]