diff --git a/Sources/AsyncHTTPClient/ConnectionPool/HTTPConnectionPool+Factory.swift b/Sources/AsyncHTTPClient/ConnectionPool/HTTPConnectionPool+Factory.swift
index f26fc8c08..2d8a17496 100644
--- a/Sources/AsyncHTTPClient/ConnectionPool/HTTPConnectionPool+Factory.swift
+++ b/Sources/AsyncHTTPClient/ConnectionPool/HTTPConnectionPool+Factory.swift
@@ -574,15 +574,17 @@ extension HTTPConnectionPool.ConnectionFactory {
         }
 
         var tlsConfig = self.tlsConfiguration
-        switch self.clientConfiguration.httpVersion.configuration {
-        case .automatic:
-            // since we can support h2, we need to advertise this in alpn
-            // "ProtocolNameList" contains the list of protocols advertised by the
-            // client, in descending order of preference.
-            // https://datatracker.ietf.org/doc/html/rfc7301#section-3.1
-            tlsConfig.applicationProtocols = ["h2", "http/1.1"]
-        case .http1Only:
-            tlsConfig.applicationProtocols = ["http/1.1"]
+        if tlsConfig.applicationProtocols.isEmpty {
+            switch self.clientConfiguration.httpVersion.configuration {
+            case .automatic:
+                // since we can support h2, we need to advertise this in alpn
+                // "ProtocolNameList" contains the list of protocols advertised by the
+                // client, in descending order of preference.
+                // https://datatracker.ietf.org/doc/html/rfc7301#section-3.1
+                tlsConfig.applicationProtocols = ["h2", "http/1.1"]
+            case .http1Only:
+                tlsConfig.applicationProtocols = ["http/1.1"]
+            }
         }
 
         #if canImport(Network)