diff --git a/spring-expression/src/main/java/org/springframework/expression/BeanResolver.java b/spring-expression/src/main/java/org/springframework/expression/BeanResolver.java
index decb1e0ca8..f6fa6e37f1 100644
--- a/spring-expression/src/main/java/org/springframework/expression/BeanResolver.java
+++ b/spring-expression/src/main/java/org/springframework/expression/BeanResolver.java
@@ -25,6 +25,7 @@ package org.springframework.expression;
  * @author Andy Clement
  * @since 3.0.3
  */
+@FunctionalInterface
 public interface BeanResolver {
 
 	/**
diff --git a/spring-expression/src/main/java/org/springframework/expression/ConstructorExecutor.java b/spring-expression/src/main/java/org/springframework/expression/ConstructorExecutor.java
index 5af02af1ee..363506b951 100644
--- a/spring-expression/src/main/java/org/springframework/expression/ConstructorExecutor.java
+++ b/spring-expression/src/main/java/org/springframework/expression/ConstructorExecutor.java
@@ -37,6 +37,7 @@ package org.springframework.expression;
  * @see ConstructorResolver
  * @see MethodExecutor
  */
+@FunctionalInterface
 public interface ConstructorExecutor {
 
 	/**
diff --git a/spring-expression/src/main/java/org/springframework/expression/MethodExecutor.java b/spring-expression/src/main/java/org/springframework/expression/MethodExecutor.java
index 170914e456..6d717cd4b0 100644
--- a/spring-expression/src/main/java/org/springframework/expression/MethodExecutor.java
+++ b/spring-expression/src/main/java/org/springframework/expression/MethodExecutor.java
@@ -36,6 +36,7 @@ package org.springframework.expression;
  * @see MethodResolver
  * @see ConstructorExecutor
  */
+@FunctionalInterface
 public interface MethodExecutor {
 
 	/**
diff --git a/spring-expression/src/main/java/org/springframework/expression/MethodResolver.java b/spring-expression/src/main/java/org/springframework/expression/MethodResolver.java
index 9d8c0bbaf0..9fb9137c8e 100644
--- a/spring-expression/src/main/java/org/springframework/expression/MethodResolver.java
+++ b/spring-expression/src/main/java/org/springframework/expression/MethodResolver.java
@@ -34,6 +34,7 @@ import org.springframework.lang.Nullable;
  * @see MethodExecutor
  * @see ConstructorResolver
  */
+@FunctionalInterface
 public interface MethodResolver {
 
 	/**