diff --git a/core/src/main/java/com/graphhopper/storage/MMapDataAccess.java b/core/src/main/java/com/graphhopper/storage/MMapDataAccess.java
index 330b3b95473..b9bf24276c1 100644
--- a/core/src/main/java/com/graphhopper/storage/MMapDataAccess.java
+++ b/core/src/main/java/com/graphhopper/storage/MMapDataAccess.java
@@ -65,7 +65,7 @@ public final class MMapDataAccess extends AbstractDataAccess {
         this.allowWrites = allowWrites;
     }
 
-    private static MethodHandle getByteBufferCleaner() {
+    static MethodHandle getByteBufferCleaner() {
         try {
             Class<?> unsafeClass = Class.forName("sun.misc.Unsafe");
             Lookup lookup = MethodHandles.privateLookupIn(unsafeClass, MethodHandles.lookup());
diff --git a/core/src/test/java/com/graphhopper/storage/MMapDataAccessTest.java b/core/src/test/java/com/graphhopper/storage/MMapDataAccessTest.java
index 1082e3d9a98..fa8876270c1 100644
--- a/core/src/test/java/com/graphhopper/storage/MMapDataAccessTest.java
+++ b/core/src/test/java/com/graphhopper/storage/MMapDataAccessTest.java
@@ -19,6 +19,9 @@
 
 import org.junit.jupiter.api.Test;
 
+import java.lang.invoke.MethodHandle;
+import java.nio.ByteBuffer;
+
 import static org.junit.jupiter.api.Assertions.*;
 
 /**
@@ -59,4 +62,17 @@ public void textMixMMAP2RAM() {
         assertEquals(123, da.getInt(7 * 4));
         da.close();
     }
+
+    @Test
+    public void testByteBufferCleaner() {
+        MethodHandle bufferCleaner = MMapDataAccess.getByteBufferCleaner();
+        assertNotNull(bufferCleaner);
+        try {
+            bufferCleaner.invokeExact(ByteBuffer.allocate(10));
+            fail("Cleaner invocation should fail for a non-direct buffer");
+        } catch (Throwable t) {
+            assertInstanceOf(IllegalArgumentException.class, t);
+            assertEquals("buffer is non-direct", t.getMessage());
+        }
+    }
 }