diff --git a/examples/cluster.c b/examples/cluster.c
index 4d6d98c..d80f11a 100644
--- a/examples/cluster.c
+++ b/examples/cluster.c
@@ -99,14 +99,26 @@ int main(int argc, char **argv) {
     }
 
     if ((can_if = hexagram_can_if_open(argv[1])) == NULL) {
+        perror("hexagram_can_if_open()");
+
         return 1;
     }
 
     if ((window = hexagram_window_new_x11(NULL, width, height)) == NULL) {
+        perror("hexagram_window_new_x11()");
+
         return 1;
     }
 
     if ((cluster = hexagram_cluster_new(width, height)) == NULL) {
+        perror("hexagram_cluster_new()");
+
+        return 1;
+    }
+
+    if (hexagram_cluster_filter_can_if(can_if) < 0) {
+        perror("hexagram_cluster_filter_can_if()");
+
         return 1;
     }