diff --git a/src/nejo_idx.py b/src/nejo_idx.py
index 94b43e3d5fcf40262113b579c969a0ebe8bb1776..ddc57fbe511ff1555174e124faf3851a94d2add6 100755
--- a/src/nejo_idx.py
+++ b/src/nejo_idx.py
@@ -43,6 +43,9 @@ class NeighborJoining:
       for j in range(0,i):
         if i < self._num_of_taxa:
           dist = dm.distance(i,j)
+          #for andi:
+          if str(dist) in ["nan"]:
+            dist = 1.0
           assert dist >= 0
         else:
           dist = None
diff --git a/src/parser.py b/src/parser.py
index 0724f24b2b4698c1ce63ee7f932698f0910209dc..ed90591ddda846877fdfda2e59eba6805d50f19a 100644
--- a/src/parser.py
+++ b/src/parser.py
@@ -31,6 +31,9 @@ def parse_command_line():
                        "NJ-tree (derived from the distances delivered by\n"
                        "the corresponding tool) will be compared to the\n"
                        "reference tree.\n"
+                       "The genome names will be cut to 10 characters. \n"
+                       "The reference tree must contain the \n"
+                       "exact genome names resulting\n"
                        "For datafiles without reference and if at least\n"
                        "two tools have been specified, the resulting\n"
                        "NJ-trees are compared against each other."