diff --git a/spring-core/src/main/java/org/springframework/util/LinkedCaseInsensitiveMap.java b/spring-core/src/main/java/org/springframework/util/LinkedCaseInsensitiveMap.java
index a916f1d856..4689d53ee1 100644
--- a/spring-core/src/main/java/org/springframework/util/LinkedCaseInsensitiveMap.java
+++ b/spring-core/src/main/java/org/springframework/util/LinkedCaseInsensitiveMap.java
@@ -227,7 +227,13 @@ public class LinkedCaseInsensitiveMap<V> implements Map<String, V>, Serializable
 	public V computeIfAbsent(String key, Function<? super String, ? extends V> mappingFunction) {
 		String oldKey = this.caseInsensitiveKeys.putIfAbsent(convertKey(key), key);
 		if (oldKey != null) {
-			return this.targetMap.get(oldKey);
+			V oldKeyValue = this.targetMap.get(oldKey);
+			if (oldKeyValue != null) {
+				return oldKeyValue;
+			}
+			else {
+				key = oldKey;
+			}
 		}
 		return this.targetMap.computeIfAbsent(key, mappingFunction);
 	}
diff --git a/spring-core/src/test/java/org/springframework/util/LinkedCaseInsensitiveMapTests.java b/spring-core/src/test/java/org/springframework/util/LinkedCaseInsensitiveMapTests.java
index f006b0baae..9f50d9d1e9 100644
--- a/spring-core/src/test/java/org/springframework/util/LinkedCaseInsensitiveMapTests.java
+++ b/spring-core/src/test/java/org/springframework/util/LinkedCaseInsensitiveMapTests.java
@@ -102,6 +102,8 @@ class LinkedCaseInsensitiveMapTests {
 
 		assertThat(map.put("null", null)).isNull();
 		assertThat(map.putIfAbsent("NULL", "value")).isNull();
+		assertThat(map.put("null", null)).isEqualTo("value");
+		assertThat(map.computeIfAbsent("NULL", s -> "value")).isEqualTo("value");
 		assertThat(map.get("null")).isEqualTo("value");
 	}