diff --git a/wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/sq/CertificationSet.kt b/wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/sq/CertificationSet.kt
index 3929e097..c1d397e6 100644
--- a/wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/sq/CertificationSet.kt
+++ b/wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/sq/CertificationSet.kt
@@ -21,7 +21,11 @@ class CertificationSet(
         certifications: Map<String?, List<Certification>>) {
 
     init {
-        certifications.forEach { (t, u) -> _certifications[t] = u.toMutableList() }
+        certifications.forEach { (_, certifications) ->
+            certifications.forEach {
+                add(it)
+            }
+        }
     }
 
     private val _certifications: MutableMap<String?, MutableList<Certification>> = mutableMapOf()