diff --git a/cronexpr_next.go b/cronexpr_next.go
index 169c900..1d627b4 100644
--- a/cronexpr_next.go
+++ b/cronexpr_next.go
@@ -236,7 +236,7 @@ func (expr *Expression) calculateActualDaysOfMonth(year, month int) []int {
 		//  offset : (7 - day_of_week_of_1st_day_of_month)
 		//  target : 1 + (7 * week_of_month) + (offset + day_of_week) % 7
 		for v := range expr.daysOfWeek {
-			w := dowNormalizedOffsets[offset%7+v]
+			w := dowNormalizedOffsets[(offset+v)%7]
 			actualDaysOfMonthMap[w[0]] = true
 			actualDaysOfMonthMap[w[1]] = true
 			actualDaysOfMonthMap[w[2]] = true
diff --git a/cronexpr_test.go b/cronexpr_test.go
index 32467fb..3692227 100644
--- a/cronexpr_test.go
+++ b/cronexpr_test.go
@@ -106,8 +106,17 @@ var crontests = []crontest{
 			{"2013-12-30 00:30:00", "Mon 2014-01-06 00:00"},
 		},
 	},
+	{
+		"0 0 * * friday",
+		"Mon 2006-01-02 15:04",
+		[]crontimes{
+			{"2013-01-01 00:00:00", "Fri 2013-01-04 00:00"},
+			{"2013-01-28 00:00:00", "Fri 2013-02-01 00:00"},
+			{"2013-12-30 00:30:00", "Fri 2014-01-03 00:00"},
+		},
+	},
 
-	// Specific weekdays of week
+	// Specific days of week
 	{
 		"0 0 * * 6#5",
 		"Mon 2006-01-02 15:04",