diff --git a/spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java b/spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java
index e7d156f0ca..284bc2163b 100644
--- a/spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java
+++ b/spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -451,11 +451,10 @@ final class HierarchicalUriComponents extends UriComponents {
 		UriTemplateVariables queryVariables = new QueryUriTemplateVariables(variables);
 		this.queryParams.forEach((key, values) -> {
 			String name = expandUriComponent(key, queryVariables, this.variableEncoder);
-			List<String> expandedValues = result.getOrDefault(name, new ArrayList<>(values.size()));
+			List<String> expandedValues = result.computeIfAbsent(name, k -> new ArrayList<>(values.size()));
 			for (String value : values) {
 				expandedValues.add(expandUriComponent(value, queryVariables, this.variableEncoder));
 			}
-			result.put(name, expandedValues);
 		});
 		return CollectionUtils.unmodifiableMultiValueMap(result);
 	}
diff --git a/spring-web/src/test/java/org/springframework/web/util/UriComponentsBuilderTests.java b/spring-web/src/test/java/org/springframework/web/util/UriComponentsBuilderTests.java
index 6376a680db..695d48f49d 100644
--- a/spring-web/src/test/java/org/springframework/web/util/UriComponentsBuilderTests.java
+++ b/spring-web/src/test/java/org/springframework/web/util/UriComponentsBuilderTests.java
@@ -629,18 +629,15 @@ class UriComponentsBuilderTests {
 		assertThat(uri.toString()).isEqualTo("ws://example.org:7777/path?q=1#foo");
 	}
 
-	@ParameterizedTest
+	@ParameterizedTest // gh-34783
 	@EnumSource
-	void parseBuildAndExpandHierarchicalWithDuplicateQueryKeys(ParserType parserType) {
-		UriComponents result = UriComponentsBuilder.fromUriString("/?{pk1}={pv1}&{pk2}={pv2}", parserType)
+	void parseBuildAndExpandQueryParamWithSameName(ParserType parserType) {
+		UriComponents result = UriComponentsBuilder
+				.fromUriString("/?{pk1}={pv1}&{pk2}={pv2}", parserType)
 				.buildAndExpand("k1", "v1", "k1", "v2");
-		assertThat(result.getQuery()).isEqualTo("k1=v1&k1=v2");
-		assertThat(result.getQueryParams().get("k1")).containsExactly("v1", "v2");
 
-		UriComponents result2 = UriComponentsBuilder.fromUriString("/?{pk1}={pv1}&{pk2}={pv2}", parserType)
-				.buildAndExpand(Map.of("pk1", "k1", "pv1", "v1", "pk2", "k1", "pv2", "v2"));
-		assertThat(result2.getQuery()).isEqualTo("k1=v1&k1=v2");
-		assertThat(result.getQueryParams().get("k1")).containsExactly("v1", "v2");
+		assertThat(result.getQuery()).isEqualTo("k1=v1&k1=v2");
+		assertThat(result.getQueryParams()).containsExactly(Map.entry("k1", List.of("v1", "v2")));
 	}
 
 	@ParameterizedTest