diff --git a/esbo_etc/classes/Entry.py b/esbo_etc/classes/Entry.py
index 48632a2..b313b20 100644
--- a/esbo_etc/classes/Entry.py
+++ b/esbo_etc/classes/Entry.py
@@ -82,7 +82,7 @@ class Entry(object):
             else:
                 return "Expected parameter '" + name + "' with unit '" + unit.to_string() + "' but got no unit."
         if not attr.unit.is_equivalent(unit):
-            return "Expected parameter '" + name + "' with unit equivalent to'" + unit.to_string() + \
+            return "Expected parameter '" + name + "' with unit equivalent to '" + unit.to_string() + \
                    "' but got unit '" + attr.unit.to_string() + "'."
         return None