2 files changed, 8 insertions, 2 deletions
diff --git a/src/main/java/org/zwobble/mammoth/internal/util/MammothSets.java b/src/main/java/org/zwobble/mammoth/internal/util/MammothSets.java
index 87f7bbe..4f06efc 100644
--- a/src/main/java/org/zwobble/mammoth/internal/util/MammothSets.java
+++ b/src/main/java/org/zwobble/mammoth/internal/util/MammothSets.java
@@ -24,6 +24,12 @@ public class MammothSets {
         return set;
     }
 
+    public static <T> Set<T> difference(Set<? extends T> set1, Set<? extends T> set2) {
+        HashSet<T> result = new HashSet<>(set1);
+        result.removeAll(set2);
+        return result;
+    }
+
     public static <T> Set<T> toSet(Iterable<T> iterable) {
         return stream(iterable).collect(Collectors.toSet());
     }
diff --git a/src/test/java/org/zwobble/mammoth/tests/DeepReflectionMatcher.java b/src/test/java/org/zwobble/mammoth/tests/DeepReflectionMatcher.java
index 5f26b42..35175d6 100644
--- a/src/test/java/org/zwobble/mammoth/tests/DeepReflectionMatcher.java
+++ b/src/test/java/org/zwobble/mammoth/tests/DeepReflectionMatcher.java
@@ -1,10 +1,10 @@
 package org.zwobble.mammoth.tests;
 
-import com.google.common.collect.Sets;
 import org.hamcrest.Description;
 import org.hamcrest.Matcher;
 import org.hamcrest.Matchers;
 import org.hamcrest.TypeSafeDiagnosingMatcher;
+import org.zwobble.mammoth.internal.util.MammothSets;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
@@ -143,7 +143,7 @@ public class DeepReflectionMatcher<T> extends TypeSafeDiagnosingMatcher<T> {
     }
 
     private static boolean handleExtraElements(String path, Map<?, ?> expected, Map<?, ?> actual, Description mismatchDescription, String prefix) {
-        Sets.SetView<?> extraElements = Sets.difference(actual.keySet(), expected.keySet());
+        Set<?> extraElements = MammothSets.difference(actual.keySet(), expected.keySet());
         if (!extraElements.isEmpty()) {
             appendPath(mismatchDescription, path);
             mismatchDescription.appendText(prefix +