diff --git a/or/orlib01.cpp b/or/orlib01.cpp
index 40914541f..450d82900 100755
--- a/or/orlib01.cpp
+++ b/or/orlib01.cpp
@@ -33,7 +33,7 @@ const int TOrdine_form::find_period(const TDate& dc)
 	for (int i = last; i >= 0; i--)
 	{
 		TDate& dt = (TDate&)*_date_array->objptr(i);
-		if (dc > dt)
+		if (dc > dt && i < last)
 			return i + 1;
 	}
   return -1;