diff --git a/src/main/java/org/scion/internal/MultiMap.java b/src/main/java/org/scion/internal/MultiMap.java
index 0019d61cd..9e2707fdb 100644
--- a/src/main/java/org/scion/internal/MultiMap.java
+++ b/src/main/java/org/scion/internal/MultiMap.java
@@ -20,30 +20,18 @@ public class MultiMap<K, V> {
   private final HashMap<K, ArrayList<V>> map = new HashMap<>();
 
   public void put(K key, V value) {
-    ArrayList<V> entry = map.get(key);
-    if (entry == null) {
-      entry = new ArrayList<>();
-      map.put(key, entry);
-    }
-    entry.add(value);
+    map.computeIfAbsent(key, k -> new ArrayList<>()).add(value);
   }
 
-  public ArrayList<V> get(K key) {
-    return map.get(key);
+  public List<V> get(K key) {
+    ArrayList<V> result = map.get(key);
+    return result == null ? Collections.emptyList() : result;
   }
 
   public boolean contains(K key) {
     return map.containsKey(key);
   }
 
-  public Set<Map.Entry<K, ArrayList<V>>> entrySet() {
-    return map.entrySet();
-  }
-
-  public Collection<ArrayList<V>> values() {
-    return map.values();
-  }
-
   public boolean isEmpty() {
     return map.isEmpty();
   }
diff --git a/src/main/java/org/scion/internal/Segments.java b/src/main/java/org/scion/internal/Segments.java
index ef2afd9b6..10864f246 100644
--- a/src/main/java/org/scion/internal/Segments.java
+++ b/src/main/java/org/scion/internal/Segments.java
@@ -239,11 +239,8 @@ private static List<Daemon.Path> combineTwoSegments(
     List<Daemon.Path> paths = new ArrayList<>();
     for (Seg.PathSegment pathSegment0 : segments0) {
       long middleIsdAs = getOtherIsdAs(srcIsdAs, pathSegment0);
-      ArrayList<Seg.PathSegment> segmentList1 = segmentsMap1.get(middleIsdAs);
-      if (segmentList1 != null) {
-        for (Seg.PathSegment pathSegment1 : segmentList1) {
-          paths.add(buildPath(brLookup, pathSegment0, pathSegment1));
-        }
+      for (Seg.PathSegment pathSegment1 : segmentsMap1.get(middleIsdAs)) {
+        paths.add(buildPath(brLookup, pathSegment0, pathSegment1));
       }
     }
     return paths;
@@ -263,9 +260,9 @@ private static List<Daemon.Path> combineThreeSegments(
     List<Daemon.Path> paths = new ArrayList<>();
     for (Seg.PathSegment pathSeg : segmentsCore) {
       long[] endIAs = getEndingIAs(pathSeg);
-      if (upSegments.get(endIAs[0]) != null && downSegments.get(endIAs[1]) != null) {
+      if (upSegments.contains(endIAs[0]) && downSegments.contains(endIAs[1])) {
         buildPath(paths, upSegments.get(endIAs[0]), pathSeg, downSegments.get(endIAs[1]), brLookup);
-      } else if (upSegments.get(endIAs[1]) != null && downSegments.get(endIAs[0]) != null) {
+      } else if (upSegments.contains(endIAs[1]) && downSegments.contains(endIAs[0])) {
         buildPath(paths, upSegments.get(endIAs[1]), pathSeg, downSegments.get(endIAs[0]), brLookup);
       }
     }
diff --git a/src/test/java/org/scion/api/DatagramSocketApiCompletenessTest.java b/src/test/java/org/scion/api/DatagramSocketApiCompletenessTest.java
index d31c44af3..7d2f7f789 100644
--- a/src/test/java/org/scion/api/DatagramSocketApiCompletenessTest.java
+++ b/src/test/java/org/scion/api/DatagramSocketApiCompletenessTest.java
@@ -40,7 +40,6 @@ void testApiCompleteness() {
       }
       List<Method> matches = methods.get(required.getName());
       boolean foundImplementation = false;
-      assertNotNull(matches, "Method not found: " + required);
       assertFalse(matches.isEmpty(), "Method not found: " + required);
       for (Method implemented : matches) {
         if (required.getParameterCount() == implemented.getParameterCount()) {
diff --git a/src/test/java/org/scion/internal/MultiMapTest.java b/src/test/java/org/scion/internal/MultiMapTest.java
index 6bf7d54d1..f6a773042 100644
--- a/src/test/java/org/scion/internal/MultiMapTest.java
+++ b/src/test/java/org/scion/internal/MultiMapTest.java
@@ -14,7 +14,71 @@
 
 package org.scion.internal;
 
-import org.junit.jupiter.api.Disabled;
+import static org.junit.jupiter.api.Assertions.*;
 
-@Disabled
-public class MultiMapTest {}
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+class MultiMapTest {
+
+  private static class Pair {
+    int i;
+    String s;
+
+    Pair(int i, String s) {
+      this.i = i;
+      this.s = s;
+    }
+  }
+
+  @Test
+  void testSmoke() {
+    MultiMap<Integer, String> map = new MultiMap<>();
+    ArrayList<Pair> list = new ArrayList<>();
+    for (int i = 0; i < 1000; i++) {
+      // Use duplicate keys as well as duplicate values
+      Pair p = new Pair(i % 10, Integer.toString(i % 100));
+      map.put(p.i, p.s);
+      list.add(p);
+    }
+
+    assertFalse(map.isEmpty());
+
+    for (Pair p : list) {
+      assertTrue(map.contains(p.i));
+      List<String> entries = map.get(p.i);
+      assertEquals(100, entries.size());
+      int matches = 0;
+      int identity = 0;
+      for (String s : entries) {
+        assertEquals(p.i, Integer.parseInt(s) % 10);
+        if (p.s.equals(s)) {
+          matches++;
+        }
+        if (p.s == s) {
+          identity++;
+        }
+      }
+      assertEquals(10, matches);
+      assertEquals(1, identity);
+    }
+
+    map.clear();
+    assertTrue(map.isEmpty());
+    assertFalse(map.contains(0));
+    assertNotNull(map.get(0));
+    assertTrue(map.get(0).isEmpty());
+  }
+
+  @Test
+  void testEmptyMap() {
+    // Check that basic function don´t fail on empty map
+    MultiMap<Integer, String> map = new MultiMap<>();
+    assertTrue(map.isEmpty());
+    // assertEquals(0, map.size());
+    assertFalse(map.contains(0));
+    assertNotNull(map.get(0));
+    assertTrue(map.get(0).isEmpty());
+  }
+}