diff --git a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/types/ExpressionBase.java b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/types/ExpressionBase.java
index 7a92e11c55..27509daaef 100644
--- a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/types/ExpressionBase.java
+++ b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/types/ExpressionBase.java
@@ -30,7 +30,7 @@ public abstract class ExpressionBase<T> implements Expression<T> {
 
   @Nullable private transient volatile String toString;
 
-  @Nullable private transient volatile Integer hashCode;
+  private transient volatile int hashCode;
 
   public ExpressionBase(Class<? extends T> type) {
     this.type = type;
@@ -43,10 +43,12 @@ public final Class<? extends T> getType() {
 
   @Override
   public final int hashCode() {
-    if (hashCode == null) {
-      hashCode = accept(HashCodeVisitor.DEFAULT, null);
+    var hash = hashCode;
+    if (hash == 0) {
+      hash = accept(HashCodeVisitor.DEFAULT, null);
+      hashCode = hash;
     }
-    return hashCode;
+    return hash;
   }
 
   @Override
diff --git a/querydsl-libraries/querydsl-core/src/test/java/com/querydsl/core/serialization/SerializerBaseTest.java b/querydsl-libraries/querydsl-core/src/test/java/com/querydsl/core/serialization/SerializerBaseTest.java
index 1faea6e194..a80aca759d 100644
--- a/querydsl-libraries/querydsl-core/src/test/java/com/querydsl/core/serialization/SerializerBaseTest.java
+++ b/querydsl-libraries/querydsl-core/src/test/java/com/querydsl/core/serialization/SerializerBaseTest.java
@@ -13,6 +13,8 @@
  */
 package com.querydsl.core.serialization;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 import com.querydsl.core.types.ConstantImpl;
 import com.querydsl.core.types.ExpressionUtils;
 import com.querydsl.core.types.JavaTemplates;
@@ -38,4 +40,38 @@ void test() {
     //  custom
     serializer.handle(ExpressionUtils.template(Object.class, "xxx", ConstantImpl.create("")));
   }
+
+  /**
+   * Constants are labelled by identity, so two equal but distinct instances are bound as two
+   * separate parameters. Boxed values outside the {@link Long} cache are distinct instances today;
+   * once the JDK migrates the wrappers to value classes (JEP 401) {@code ==} becomes state based
+   * and this collapses to a single label.
+   */
+  @Test
+  void equalButDistinctConstantsGetDistinctLabels() {
+    var serializer = new DummySerializer(new JavaTemplates());
+    Long first = 1000L;
+    Long second = 1000L;
+    assertThat(first).isNotSameAs(second).isEqualTo(second);
+
+    serializer.handle((Object) first);
+    serializer.handle((Object) second);
+
+    assertThat(serializer.getConstants()).containsExactly(first, second);
+    assertThat(serializer.getConstantToLabel()).hasSize(2);
+    assertThat(serializer).hasToString("a1a2");
+  }
+
+  @Test
+  void repeatedConstantInstanceReusesLabel() {
+    var serializer = new DummySerializer(new JavaTemplates());
+    Long value = 1000L;
+
+    serializer.handle((Object) value);
+    serializer.handle((Object) value);
+
+    assertThat(serializer.getConstants()).containsExactly(value, value);
+    assertThat(serializer.getConstantToLabel()).hasSize(1);
+    assertThat(serializer).hasToString("a1a1");
+  }
 }