diff --git a/server/src/test/java/org/elasticsearch/BuildTests.java b/server/src/test/java/org/elasticsearch/BuildTests.java
index 12af1d31841..f1d48c08b39 100644
--- a/server/src/test/java/org/elasticsearch/BuildTests.java
+++ b/server/src/test/java/org/elasticsearch/BuildTests.java
@@ -162,8 +162,9 @@ public class BuildTests extends ESTestCase {
         EqualsHashCodeTestUtils.checkEqualsAndHashCode(new WriteableBuild(new Build(
                 randomFrom(Build.Flavor.values()), randomFrom(Build.Type.values()),
                 randomAlphaOfLength(6), randomAlphaOfLength(6), randomBoolean(), randomAlphaOfLength(6))),
-            b -> copyWriteable(b, writableRegistry(), WriteableBuild::new, Version.CURRENT),
-            b -> {
+            // Note: the cast of the Copy- and MutateFunction is needed for some IDE (specifically Eclipse 4.10.0) to infer the right type
+            (WriteableBuild b) -> copyWriteable(b, writableRegistry(), WriteableBuild::new, Version.CURRENT),
+            (WriteableBuild b) -> {
                 switch (randomIntBetween(1, 6)) {
                     case 1:
                         return new WriteableBuild(new Build(