diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/HttpServerUpgradeHandler.java b/codec-http/src/main/java/io/netty/handler/codec/http/HttpServerUpgradeHandler.java
index f1f3efcb1d..2b54b0e4b2 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/HttpServerUpgradeHandler.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/HttpServerUpgradeHandler.java
@@ -14,9 +14,6 @@
  */
 package io.netty.handler.codec.http;
 
-import static io.netty.util.AsciiString.containsContentEqualsIgnoreCase;
-import static io.netty.util.AsciiString.containsAllContentEqualsIgnoreCase;
-
 import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
@@ -30,7 +27,10 @@ import java.util.List;
 
 import static io.netty.handler.codec.http.HttpResponseStatus.SWITCHING_PROTOCOLS;
 import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
+import static io.netty.util.AsciiString.containsAllContentEqualsIgnoreCase;
+import static io.netty.util.AsciiString.containsContentEqualsIgnoreCase;
 import static io.netty.util.internal.ObjectUtil.checkNotNull;
+import static io.netty.util.internal.StringUtil.COMMA;
 
 /**
  * A server-side handler that receives HTTP requests and optionally performs a protocol switch if
@@ -284,16 +284,23 @@ public class HttpServerUpgradeHandler extends HttpObjectAggregator {
         }
 
         // Make sure the CONNECTION header is present.
-        CharSequence connectionHeader = request.headers().get(HttpHeaderNames.CONNECTION);
-        if (connectionHeader == null) {
+        List<String> connectionHeaderValues = request.headers().getAll(HttpHeaderNames.CONNECTION);
+
+        if (connectionHeaderValues == null) {
             return false;
         }
 
+        final StringBuilder concatenatedConnectionValue = new StringBuilder(connectionHeaderValues.size() * 10);
+        for (CharSequence connectionHeaderValue : connectionHeaderValues) {
+            concatenatedConnectionValue.append(connectionHeaderValue).append(COMMA);
+        }
+        concatenatedConnectionValue.setLength(concatenatedConnectionValue.length() - 1);
+
         // Make sure the CONNECTION header contains UPGRADE as well as all protocol-specific headers.
         Collection<CharSequence> requiredHeaders = upgradeCodec.requiredUpgradeHeaders();
-        List<CharSequence> values = splitHeader(connectionHeader);
+        List<CharSequence> values = splitHeader(concatenatedConnectionValue);
         if (!containsContentEqualsIgnoreCase(values, HttpHeaderNames.UPGRADE) ||
-            !containsAllContentEqualsIgnoreCase(values, requiredHeaders)) {
+                !containsAllContentEqualsIgnoreCase(values, requiredHeaders)) {
             return false;
         }
 
diff --git a/codec-http2/src/test/java/io/netty/handler/codec/http2/CleartextHttp2ServerUpgradeHandlerTest.java b/codec-http2/src/test/java/io/netty/handler/codec/http2/CleartextHttp2ServerUpgradeHandlerTest.java
index a544054b66..129f62d757 100644
--- a/codec-http2/src/test/java/io/netty/handler/codec/http2/CleartextHttp2ServerUpgradeHandlerTest.java
+++ b/codec-http2/src/test/java/io/netty/handler/codec/http2/CleartextHttp2ServerUpgradeHandlerTest.java
@@ -42,8 +42,15 @@ import org.junit.Test;
 import java.util.ArrayList;
 import java.util.List;
 
-import static org.junit.Assert.*;
-import static org.mockito.Mockito.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
 
 /**
  * Tests for {@link CleartextHttp2ServerUpgradeHandler}
@@ -112,47 +119,35 @@ public class CleartextHttp2ServerUpgradeHandlerTest {
 
     @Test
     public void upgrade() throws Exception {
-        setUpServerChannel();
-
         String upgradeString = "GET / HTTP/1.1\r\n" +
-                               "Host: example.com\r\n" +
-                               "Connection: Upgrade, HTTP2-Settings\r\n" +
-                               "Upgrade: h2c\r\n" +
-                               "HTTP2-Settings: AAMAAABkAAQAAP__\r\n\r\n";
-        ByteBuf upgrade = Unpooled.copiedBuffer(upgradeString, CharsetUtil.US_ASCII);
+                "Host: example.com\r\n" +
+                "Connection: Upgrade, HTTP2-Settings\r\n" +
+                "Upgrade: h2c\r\n" +
+                "HTTP2-Settings: AAMAAABkAAQAAP__\r\n\r\n";
+        validateClearTextUpgrade(upgradeString);
+    }
 
-        assertFalse(channel.writeInbound(upgrade));
+    @Test
+    public void upgradeWithMultipleConnectionHeaders() {
+        String upgradeString = "GET / HTTP/1.1\r\n" +
+                "Host: example.com\r\n" +
+                "Connection: keep-alive\r\n" +
+                "Connection: Upgrade, HTTP2-Settings\r\n" +
+                "Upgrade: h2c\r\n" +
+                "HTTP2-Settings: AAMAAABkAAQAAP__\r\n\r\n";
+        validateClearTextUpgrade(upgradeString);
+    }
 
-        assertEquals(1, userEvents.size());
-
-        Object userEvent = userEvents.get(0);
-        assertTrue(userEvent instanceof UpgradeEvent);
-        assertEquals("h2c", ((UpgradeEvent) userEvent).protocol());
-        ReferenceCountUtil.release(userEvent);
-
-        assertEquals(100, http2ConnectionHandler.connection().local().maxActiveStreams());
-        assertEquals(65535, http2ConnectionHandler.connection().local().flowController().initialWindowSize());
-
-        assertEquals(1, http2ConnectionHandler.connection().numActiveStreams());
-        assertNotNull(http2ConnectionHandler.connection().stream(1));
-
-        Http2Stream stream = http2ConnectionHandler.connection().stream(1);
-        assertEquals(State.HALF_CLOSED_REMOTE, stream.state());
-        assertFalse(stream.isHeadersSent());
-
-        String expectedHttpResponse = "HTTP/1.1 101 Switching Protocols\r\n" +
-                "connection: upgrade\r\n" +
-                "upgrade: h2c\r\n\r\n";
-        ByteBuf responseBuffer = channel.readOutbound();
-        assertEquals(expectedHttpResponse, responseBuffer.toString(CharsetUtil.UTF_8));
-        responseBuffer.release();
-
-        // Check that the preface was send (a.k.a the settings frame)
-        ByteBuf settingsBuffer = channel.readOutbound();
-        assertNotNull(settingsBuffer);
-        settingsBuffer.release();
-
-        assertNull(channel.readOutbound());
+    @Test
+    public void requiredHeadersInSeparateConnectionHeaders() {
+        String upgradeString = "GET / HTTP/1.1\r\n" +
+                "Host: example.com\r\n" +
+                "Connection: keep-alive\r\n" +
+                "Connection: HTTP2-Settings\r\n" +
+                "Connection: Upgrade\r\n" +
+                "Upgrade: h2c\r\n" +
+                "HTTP2-Settings: AAMAAABkAAQAAP__\r\n\r\n";
+        validateClearTextUpgrade(upgradeString);
     }
 
     @Test
@@ -254,4 +249,43 @@ public class CleartextHttp2ServerUpgradeHandlerTest {
     private static Http2Settings expectedSettings() {
         return new Http2Settings().maxConcurrentStreams(100).initialWindowSize(65535);
     }
+
+    private void validateClearTextUpgrade(String upgradeString) {
+        setUpServerChannel();
+
+        ByteBuf upgrade = Unpooled.copiedBuffer(upgradeString, CharsetUtil.US_ASCII);
+
+        assertFalse(channel.writeInbound(upgrade));
+
+        assertEquals(1, userEvents.size());
+
+        Object userEvent = userEvents.get(0);
+        assertTrue(userEvent instanceof UpgradeEvent);
+        assertEquals("h2c", ((UpgradeEvent) userEvent).protocol());
+        ReferenceCountUtil.release(userEvent);
+
+        assertEquals(100, http2ConnectionHandler.connection().local().maxActiveStreams());
+        assertEquals(65535, http2ConnectionHandler.connection().local().flowController().initialWindowSize());
+
+        assertEquals(1, http2ConnectionHandler.connection().numActiveStreams());
+        assertNotNull(http2ConnectionHandler.connection().stream(1));
+
+        Http2Stream stream = http2ConnectionHandler.connection().stream(1);
+        assertEquals(State.HALF_CLOSED_REMOTE, stream.state());
+        assertFalse(stream.isHeadersSent());
+
+        String expectedHttpResponse = "HTTP/1.1 101 Switching Protocols\r\n" +
+                "connection: upgrade\r\n" +
+                "upgrade: h2c\r\n\r\n";
+        ByteBuf responseBuffer = channel.readOutbound();
+        assertEquals(expectedHttpResponse, responseBuffer.toString(CharsetUtil.UTF_8));
+        responseBuffer.release();
+
+        // Check that the preface was send (a.k.a the settings frame)
+        ByteBuf settingsBuffer = channel.readOutbound();
+        assertNotNull(settingsBuffer);
+        settingsBuffer.release();
+
+        assertNull(channel.readOutbound());
+    }
 }