diff --git a/requirements.txt b/requirements.txt
index 66f137c9..e33778a9 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,6 +2,8 @@ Babel>=1.3
 Flask-Babel==0.11.1
 Flask-Login>=0.3.2
 Flask-Principal>=0.3.2
+singledispatch>=3.4.0.0
+backports_abc>=0.4
 Flask>=0.11
 iso-639>=0.4.5
 PyPDF2==1.26.0
@@ -10,4 +12,4 @@ requests>=2.11.1
 SQLAlchemy>=0.8.4
 tornado>=4.1
 Wand>=0.4.4
-unidecode>=0.04.19
\ No newline at end of file
+unidecode>=0.04.19