diff --git a/assignroom.go b/assignroom.go
index 3ffde12..c74f979 100644
--- a/assignroom.go
+++ b/assignroom.go
@@ -1,5 +1,9 @@
 package main
 
+import (
+	"fmt"
+)
+
 func AssignExtraRooms(rooms []RoomFolder, roomsPerNight int) {
 	latestnight := 0
 
@@ -27,3 +31,33 @@ func AssignExtraRooms(rooms []RoomFolder, roomsPerNight int) {
 		}
 	}
 }
+
+func CheckDuplicateRooms(rooms []RoomFolder) error {
+	maxnight := 0
+	maxroom := 0
+
+	for _, r := range rooms {
+		if r.Cfg.night > maxnight {
+			maxnight = r.Cfg.night
+		}
+		if r.Cfg.room > maxroom {
+			maxroom = r.Cfg.room
+		}
+	}
+
+	assignments := make([][]string, maxnight)
+	for night := range maxnight {
+		assignments[night] = make([]string, maxroom)
+	}
+
+	for _, r := range rooms {
+		if r.Cfg.night > 0 && r.Cfg.room > 0 {
+			if assignments[r.Cfg.night-1][r.Cfg.room-1] != "" {
+				return fmt.Errorf("duplicate room assignment for Room %d Night %d: %s, %s", r.Cfg.night, r.Cfg.room, assignments[r.Cfg.night][r.Cfg.room], r.Path)
+			}
+			assignments[r.Cfg.night-1][r.Cfg.room-1] = r.Path
+		}
+	}
+
+	return nil
+}
diff --git a/main.go b/main.go
index 4eec1a5..6e31911 100644
--- a/main.go
+++ b/main.go
@@ -1,6 +1,9 @@
 package main
 
-import "flag"
+import (
+	"flag"
+	"log"
+)
 
 func main() {
 	if err := mainErr(); err != nil {
@@ -23,6 +26,12 @@ func mainErr() error {
 		return err
 	}
 
+	err = CheckDuplicateRooms(roomFolders)
+	if err != nil {
+		log.Printf("Error in room assigmnents: %v", err)
+		return nil
+	}
+	
 	AssignExtraRooms(roomFolders, *roomPerNight)
 
 	// only deletes DATA/NIGHT_* folders and the CF.ini file