diff --git a/requirements.txt b/requirements.txt
index e2b29a225..8e964384d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,7 +4,7 @@ setuptools>=18.5			# Require this first, to prevent later errors
 anora>=0.1.2
 argon2-cffi>=16.1.0		# For the Argon2 password hasher option
 beautifulsoup4>=4.4
-bibtexparser>=0.6.2
+bibtexparser>=0.6.2,<1.0
 bleach>=1.5.0,<2.0.0
 coverage>=4.0.1,!=4.0.2
 #cssselect>=0.6.1               # for PyQuery