diff --git a/changelog/unreleased/SOLR-solrqueryresponse-return-types.yml b/changelog/unreleased/SOLR-solrqueryresponse-return-types.yml
new file mode 100644
index 000000000000..6b13f8f6c1a3
--- /dev/null
+++ b/changelog/unreleased/SOLR-solrqueryresponse-return-types.yml
@@ -0,0 +1,10 @@
+title: >
+  SolrQueryResponse.getResponseHeader()/addResponseHeader() are now declared to return/accept
+  SimpleOrderedMap<Object> instead of NamedList<Object>. External code compiled against the old
+  signature will get a NoSuchMethodError at runtime and must recompile.
+type: changed
+authors:
+  - name: Serhiy Bzhezytskyy
+links:
+  - name: PR#4809
+    url: https://github.com/apache/solr/pull/4809
diff --git a/solr/core/src/java/org/apache/solr/core/SolrCore.java b/solr/core/src/java/org/apache/solr/core/SolrCore.java
index 291d06eadcea..6f1c40731c6e 100644
--- a/solr/core/src/java/org/apache/solr/core/SolrCore.java
+++ b/solr/core/src/java/org/apache/solr/core/SolrCore.java
@@ -2946,7 +2946,7 @@ public void execute(SolrRequestHandler handler, SolrQueryRequest req, SolrQueryR
 
   public static void preDecorateResponse(SolrQueryRequest req, SolrQueryResponse rsp) {
     // setup response header
-    final NamedList<Object> responseHeader = new SimpleOrderedMap<>();
+    final SimpleOrderedMap<Object> responseHeader = new SimpleOrderedMap<>();
     rsp.addResponseHeader(responseHeader);
 
     rsp.addToLog(PATH, req.getContext().get(PATH));
diff --git a/solr/core/src/java/org/apache/solr/handler/component/CombinedQueryComponent.java b/solr/core/src/java/org/apache/solr/handler/component/CombinedQueryComponent.java
index 28b4a80bb6ec..5447b57a79cb 100644
--- a/solr/core/src/java/org/apache/solr/handler/component/CombinedQueryComponent.java
+++ b/solr/core/src/java/org/apache/solr/handler/component/CombinedQueryComponent.java
@@ -457,7 +457,6 @@ protected void mergeIds(ResponseBuilder rb, ShardRequest sreq) {
     if (thereArePartialResults) {
       rb.rsp
           .getResponseHeader()
-          .asShallowMap()
           .put(SolrQueryResponse.RESPONSE_HEADER_PARTIAL_RESULTS_KEY, Boolean.TRUE);
     }
     if (segmentTerminatedEarly != null) {
@@ -474,10 +473,7 @@ protected void mergeIds(ResponseBuilder rb, ShardRequest sreq) {
       } else if (!Boolean.TRUE.equals(existingSegmentTerminatedEarly) && segmentTerminatedEarly) {
         rb.rsp
             .getResponseHeader()
-            .remove(SolrQueryResponse.RESPONSE_HEADER_SEGMENT_TERMINATED_EARLY_KEY);
-        rb.rsp
-            .getResponseHeader()
-            .add(SolrQueryResponse.RESPONSE_HEADER_SEGMENT_TERMINATED_EARLY_KEY, true);
+            .put(SolrQueryResponse.RESPONSE_HEADER_SEGMENT_TERMINATED_EARLY_KEY, true);
       }
     }
     if (maxHitsTerminatedEarly) {
diff --git a/solr/core/src/java/org/apache/solr/handler/component/QueryComponent.java b/solr/core/src/java/org/apache/solr/handler/component/QueryComponent.java
index 3c8c2a7a5bdd..0cd1c0760601 100644
--- a/solr/core/src/java/org/apache/solr/handler/component/QueryComponent.java
+++ b/solr/core/src/java/org/apache/solr/handler/component/QueryComponent.java
@@ -1239,7 +1239,6 @@ protected void mergeIds(ResponseBuilder rb, ShardRequest sreq) {
     if (thereArePartialResults) {
       rb.rsp
           .getResponseHeader()
-          .asShallowMap()
           .put(SolrQueryResponse.RESPONSE_HEADER_PARTIAL_RESULTS_KEY, Boolean.TRUE);
     }
     if (segmentTerminatedEarly != null) {
@@ -1257,10 +1256,7 @@ protected void mergeIds(ResponseBuilder rb, ShardRequest sreq) {
           && Boolean.TRUE.equals(segmentTerminatedEarly)) {
         rb.rsp
             .getResponseHeader()
-            .remove(SolrQueryResponse.RESPONSE_HEADER_SEGMENT_TERMINATED_EARLY_KEY);
-        rb.rsp
-            .getResponseHeader()
-            .add(
+            .put(
                 SolrQueryResponse.RESPONSE_HEADER_SEGMENT_TERMINATED_EARLY_KEY,
                 segmentTerminatedEarly);
       }
diff --git a/solr/core/src/java/org/apache/solr/response/SolrQueryResponse.java b/solr/core/src/java/org/apache/solr/response/SolrQueryResponse.java
index 5f2b67622d63..9e3a6dcb7c81 100644
--- a/solr/core/src/java/org/apache/solr/response/SolrQueryResponse.java
+++ b/solr/core/src/java/org/apache/solr/response/SolrQueryResponse.java
@@ -258,7 +258,7 @@ public Exception getException() {
   }
 
   /** Set response header */
-  public void addResponseHeader(NamedList<Object> header) {
+  public void addResponseHeader(SimpleOrderedMap<Object> header) {
     values.add(RESPONSE_HEADER_KEY, header);
   }
 
@@ -268,10 +268,9 @@ public void removeResponseHeader() {
   }
 
   /** Response header to be logged */
-  public NamedList<Object> getResponseHeader() {
-    @SuppressWarnings("unchecked")
-    SimpleOrderedMap<Object> header = (SimpleOrderedMap<Object>) values.get(RESPONSE_HEADER_KEY);
-    return header;
+  @SuppressWarnings("unchecked")
+  public SimpleOrderedMap<Object> getResponseHeader() {
+    return (SimpleOrderedMap<Object>) values.get(RESPONSE_HEADER_KEY);
   }
 
   /** Set response */
diff --git a/solr/core/src/java/org/apache/solr/update/processor/IgnoreCommitOptimizeUpdateProcessorFactory.java b/solr/core/src/java/org/apache/solr/update/processor/IgnoreCommitOptimizeUpdateProcessorFactory.java
index 9e8eff7cb553..f4d8abb901e4 100644
--- a/solr/core/src/java/org/apache/solr/update/processor/IgnoreCommitOptimizeUpdateProcessorFactory.java
+++ b/solr/core/src/java/org/apache/solr/update/processor/IgnoreCommitOptimizeUpdateProcessorFactory.java
@@ -139,7 +139,7 @@ public void processCommit(CommitUpdateCommand cmd) throws IOException {
         IgnoreCommitOptimizeUpdateProcessorFactory.log.info(
             "{} from client application ignored with status code: 200", cmdType);
         if (responseMsg != null) {
-          NamedList<Object> responseHeader = rsp.getResponseHeader();
+          SimpleOrderedMap<Object> responseHeader = rsp.getResponseHeader();
           if (responseHeader != null) {
             responseHeader.add("msg", responseMsg);
           } else {
diff --git a/solr/core/src/test/org/apache/solr/handler/component/MockResponseBuilder.java b/solr/core/src/test/org/apache/solr/handler/component/MockResponseBuilder.java
index 241ff703fb5f..fa8bca48727d 100644
--- a/solr/core/src/test/org/apache/solr/handler/component/MockResponseBuilder.java
+++ b/solr/core/src/test/org/apache/solr/handler/component/MockResponseBuilder.java
@@ -20,7 +20,7 @@
 import java.util.List;
 import org.apache.solr.common.params.ShardParams;
 import org.apache.solr.common.params.SolrParams;
-import org.apache.solr.common.util.NamedList;
+import org.apache.solr.common.util.SimpleOrderedMap;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.response.SolrQueryResponse;
 import org.apache.solr.schema.IndexSchema;
@@ -48,7 +48,7 @@ public static MockResponseBuilder create() {
     SchemaField uniqueIdField = new SchemaField("id", new StrField());
 
     // we need this because QueryComponent adds a property to it.
-    NamedList<Object> responseHeader = new NamedList<>();
+    SimpleOrderedMap<Object> responseHeader = new SimpleOrderedMap<>();
 
     // the mock implementations
     Mockito.when(request.getSchema()).thenReturn(indexSchema);
diff --git a/solr/core/src/test/org/apache/solr/response/TestSolrQueryResponse.java b/solr/core/src/test/org/apache/solr/response/TestSolrQueryResponse.java
index 3d6fbe46e57c..b414eb5bdd7a 100644
--- a/solr/core/src/test/org/apache/solr/response/TestSolrQueryResponse.java
+++ b/solr/core/src/test/org/apache/solr/response/TestSolrQueryResponse.java
@@ -279,7 +279,7 @@ public void testException() {
   public void testResponseHeader() {
     final SolrQueryResponse response = new SolrQueryResponse();
     assertNull("responseHeader initially present", response.getResponseHeader());
-    final NamedList<Object> newValue = new SimpleOrderedMap<>();
+    final SimpleOrderedMap<Object> newValue = new SimpleOrderedMap<>();
     newValue.add("key1", "value1");
     response.add("key2", "value2");
     response.addResponseHeader(newValue);
@@ -300,7 +300,7 @@ public void testHttpCaching() {
   @Test
   public void testConvertToHEADStyleResponse() {
     final SolrQueryResponse response = new SolrQueryResponse();
-    final NamedList<Object> newValue = new SimpleOrderedMap<>();
+    final SimpleOrderedMap<Object> newValue = new SimpleOrderedMap<>();
     newValue.add("responseHeaderKey1", "value1");
     response.add("responseHeaderKey2", "value2");
     response.addResponseHeader(newValue);