diff --git a/requirements.txt b/requirements.txt
index 13a7412b..a9da4f79 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,4 +8,4 @@ tqdm==4.60.0
 colorlog==5.0.1
 emcee==3.0.2
 pybtex==0.24.0
-flex-format==0.2.2
+flex-format==0.2.6