diff --git a/server/src/test/java/org/elasticsearch/common/util/CuckooFilterTests.java b/server/src/test/java/org/elasticsearch/common/util/CuckooFilterTests.java
index 47e9081d815b6..61d2dd62c9aad 100644
--- a/server/src/test/java/org/elasticsearch/common/util/CuckooFilterTests.java
+++ b/server/src/test/java/org/elasticsearch/common/util/CuckooFilterTests.java
@@ -30,8 +30,8 @@ public class CuckooFilterTests extends AbstractWireSerializingTestCase<CuckooFil
 
     @Override
     protected CuckooFilter createTestInstance() {
-        CuckooFilter filter = new CuckooFilter(randomIntBetween(1, 100000),
-            ((float)randomIntBetween(1, 50)) / 100.0, Randomness.get());
+        CuckooFilter filter = new CuckooFilter(randomIntBetween(10000, 100000),
+            ((float)randomIntBetween(1, 20)) / 100.0, Randomness.get());
 
         int num = randomIntBetween(0, 10);
         for (int i = 0; i < num; i++) {
@@ -53,6 +53,15 @@ protected CuckooFilter mutateInstance(CuckooFilter instance) {
         for (int i = 0; i < num; i++) {
             newInstance.add(hash(randomLong()));
         }
+        int attempts = 0;
+        while (newInstance.getCount() == instance.getCount() && attempts < 100) {
+            newInstance.add(hash(randomLong()));
+            attempts += 1;
+        }
+        if (newInstance.equals(instance)) {
+            fail("Unable to mutate filter enough to generate a different version. " +
+                "Are capacity/precision defaults too low?");
+        }
         return newInstance;
     }