diff --git a/ci/requirements-2.7_DOC_BUILD.run b/ci/requirements-2.7_DOC_BUILD.run
index 854776762fdb5..507ce9ea5aac5 100644
--- a/ci/requirements-2.7_DOC_BUILD.run
+++ b/ci/requirements-2.7_DOC_BUILD.run
@@ -1,6 +1,7 @@
 ipython
 sphinx
 nbconvert
+nbformat
 matplotlib
 scipy
 lxml