diff --git a/.travis.yml b/.travis.yml
index b2c6feb7a..4c8bab708 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,7 +25,7 @@ install:
   - pip install -e .
 script:
   - coverage run --source=artiq setup.py test
-  - make -C doc/manual html || true
+  - make -C doc/manual html
   - cd misoc; python make.py -X ../soc -t artiq build-headers build-bios; cd ..
   - make -C soc/runtime
   - cd misoc; python make.py -X ../soc -t artiq build-bitstream; cd ..
diff --git a/doc/manual/conf.py b/doc/manual/conf.py
index 02a3adf23..0d8e0a5d8 100644
--- a/doc/manual/conf.py
+++ b/doc/manual/conf.py
@@ -16,6 +16,21 @@
 import sys
 import os
 
+from unittest.mock import MagicMock
+
+
+class Mock(MagicMock):
+    @classmethod
+    def __getattr__(cls, name):
+            return Mock()
+
+
+mock_modules = ["gbulb", "gi", "gi.repository", "cairoplot", "matplotlib"]
+
+for module in mock_modules:
+    sys.modules[module] = Mock()
+
+
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.