diff --git a/treetime/config.py b/treetime/config.py
index <HASH>..<HASH> 100644
--- a/treetime/config.py
+++ b/treetime/config.py
@@ -1,7 +1,7 @@
 VERBOSE = 3
 
 BIG_NUMBER = 1e10
-TINY_NUMBER = 1e-10
+TINY_NUMBER = 1e-12
 MIN_LOG = -1e8 # minimal log value
 MIN_BRANCH_LENGTH = 1e-3 # fraction of length 'one_mutation' that is used as lower cut-off for branch lengths in GTR
Setting TINY_NUMBER to 1e-<I> - important for TB