diff --git a/spring-restdocs-core/src/main/java/org/springframework/restdocs/operation/preprocess/HeadersModifyingOperationPreprocessor.java b/spring-restdocs-core/src/main/java/org/springframework/restdocs/operation/preprocess/HeadersModifyingOperationPreprocessor.java
index ef732352..bdc91f3f 100644
--- a/spring-restdocs-core/src/main/java/org/springframework/restdocs/operation/preprocess/HeadersModifyingOperationPreprocessor.java
+++ b/spring-restdocs-core/src/main/java/org/springframework/restdocs/operation/preprocess/HeadersModifyingOperationPreprocessor.java
@@ -144,7 +144,7 @@ private SetHeaderModification(String name, List<String> values) {
 
 		@Override
 		public void applyTo(HttpHeaders headers) {
-			headers.put(this.name, this.values);
+			headers.put(this.name, new ArrayList<>(this.values));
 		}
 
 	}
diff --git a/spring-restdocs-core/src/test/java/org/springframework/restdocs/operation/preprocess/HeadersModifyingOperationPreprocessorTests.java b/spring-restdocs-core/src/test/java/org/springframework/restdocs/operation/preprocess/HeadersModifyingOperationPreprocessorTests.java
index 0beaa23c..504e5167 100644
--- a/spring-restdocs-core/src/test/java/org/springframework/restdocs/operation/preprocess/HeadersModifyingOperationPreprocessorTests.java
+++ b/spring-restdocs-core/src/test/java/org/springframework/restdocs/operation/preprocess/HeadersModifyingOperationPreprocessorTests.java
@@ -73,6 +73,24 @@ void setExistingHeader() {
 			.headerSet()).contains(entry("a", Arrays.asList("alpha", "avocado")));
 	}
 
+	@Test
+	void addValueToHeaderThatWasSet() {
+		this.preprocessor.set("a", "alpha").add("a", "avocado");
+		assertThat(this.preprocessor.preprocess(createRequest()).getHeaders().headerSet())
+			.contains(entry("a", Arrays.asList("alpha", "avocado")));
+		assertThat(this.preprocessor.preprocess(createResponse()).getHeaders().headerSet())
+			.contains(entry("a", Arrays.asList("alpha", "avocado")));
+	}
+
+	@Test
+	void removeValueFromHeaderThatWasSet() {
+		this.preprocessor.set("a", "alpha", "avocado").remove("a", "alpha");
+		assertThat(this.preprocessor.preprocess(createRequest()).getHeaders().headerSet())
+			.contains(entry("a", Arrays.asList("avocado")));
+		assertThat(this.preprocessor.preprocess(createResponse()).getHeaders().headerSet())
+			.contains(entry("a", Arrays.asList("avocado")));
+	}
+
 	@Test
 	void removeNonExistentHeader() {
 		this.preprocessor.remove("a");