diff --git a/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/ClientH2StreamHandler.java b/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/ClientH2StreamHandler.java
index 6393e5991..68b22c24a 100644
--- a/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/ClientH2StreamHandler.java
+++ b/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/ClientH2StreamHandler.java
@@ -209,6 +209,9 @@ public void consumeHeader(final List<Header> headers, final boolean endStream) t
                 if (status < HttpStatus.SC_INFORMATIONAL) {
                     throw new ProtocolException("Invalid response: " + new StatusLine(response));
                 }
+                if (status < HttpStatus.SC_SUCCESS && endStream) {
+                    throw new ProtocolException("Informational response must not set END_STREAM");
+                }
                 if (status > HttpStatus.SC_CONTINUE && status < HttpStatus.SC_SUCCESS) {
                     exchangeHandler.consumeInformation(response, context);
                 }
@@ -238,6 +241,9 @@ public void consumeHeader(final List<Header> headers, final boolean endStream) t
                 responseState.set(endStream ? MessageState.COMPLETE : MessageState.BODY);
                 break;
             case BODY:
+                if (!endStream) {
+                    throw new ProtocolException("Trailer headers must set END_STREAM");
+                }
                 TrailersValidationSupport.verify(headers);
                 responseState.set(MessageState.COMPLETE);
                 exchangeHandler.streamEnd(headers);
diff --git a/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/nio/TestClientH2StreamHandler.java b/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/nio/TestClientH2StreamHandler.java
index 1df777354..739d102a5 100644
--- a/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/nio/TestClientH2StreamHandler.java
+++ b/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/nio/TestClientH2StreamHandler.java
@@ -26,12 +26,14 @@
  */
 package org.apache.hc.core5.http2.impl.nio;
 
+import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
 import org.apache.hc.core5.http.Header;
+import org.apache.hc.core5.http.HttpException;
 import org.apache.hc.core5.http.ProtocolException;
 import org.apache.hc.core5.http.impl.BasicHttpConnectionMetrics;
 import org.apache.hc.core5.http.impl.BasicHttpTransportMetrics;
@@ -117,6 +119,24 @@ void consumeTrailersWithPseudoHeaderRejected() throws Exception {
         Mockito.verify(exchangeHandler, Mockito.never()).streamEnd(Mockito.anyList());
     }
 
+    @Test
+    void informationalResponseWithEndStreamRejected() throws HttpException, IOException {
+        final List<Header> responseHeaders = Collections.singletonList(
+                new BasicHeader(":status", "103"));
+        Assertions.assertThrows(ProtocolException.class, () -> handler.consumeHeader(responseHeaders, true));
+        Mockito.verify(exchangeHandler, Mockito.never()).consumeInformation(Mockito.any(), Mockito.any());
+    }
+    @Test
+    void consumeTrailersWithoutEndStreamRejected() throws Exception {
+        final List<Header> responseHeaders = Collections.singletonList(
+                new BasicHeader(":status", "200"));
+        handler.consumeHeader(responseHeaders, false);
+
+        final List<Header> trailers = Collections.singletonList(
+                new BasicHeader("x-checksum", "abc123"));
+        Assertions.assertThrows(ProtocolException.class, () -> handler.consumeHeader(trailers, false));
+        Mockito.verify(exchangeHandler, Mockito.never()).streamEnd(Mockito.anyList());
+    }
     @Test
     void contentLengthValid() throws Exception {
         final List<Header> responseHeaders = Arrays.asList(