diff --git a/common/httpx/http11_fallback_test.go b/common/httpx/http11_fallback_test.go
new file mode 100644
index 00000000..e7626f74
--- /dev/null
+++ b/common/httpx/http11_fallback_test.go
@@ -0,0 +1,23 @@
+package httpx
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNew_HTTP11DisablesRetryableHTTP2Fallback(t *testing.T) {
+	opts := DefaultOptions
+	opts.Protocol = HTTP11
+
+	ht, err := New(&opts)
+	require.NoError(t, err)
+	require.NotNil(t, ht)
+	require.NotNil(t, ht.client)
+	require.NotNil(t, ht.client.HTTPClient)
+	require.NotNil(t, ht.client.HTTPClient2)
+
+	// Protocol pinning expectation: when forced to HTTP/1.1, retry fallback should
+	// stay on the same client/transport instead of switching to dedicated HTTP/2.
+	require.Same(t, ht.client.HTTPClient, ht.client.HTTPClient2)
+}
diff --git a/common/httpx/httpx.go b/common/httpx/httpx.go
index 039f4c4c..39a6d0ce 100644
--- a/common/httpx/httpx.go
+++ b/common/httpx/httpx.go
@@ -183,6 +183,13 @@ func New(options *Options) (*HTTPX, error) {
 		CheckRedirect: redirectFunc,
 	}, retryablehttpOptions)
 
+	// When protocol is explicitly forced to HTTP/1.1, prevent retryablehttp from
+	// falling back to its dedicated HTTP/2 client path on malformed HTTP/2 errors.
+	// Keep retries enabled, but pinned to the same HTTP/1.1 transport settings.
+	if httpx.Options.Protocol == HTTP11 {
+		httpx.client.HTTPClient2 = httpx.client.HTTPClient
+	}
+
 	transport2 := &http2.Transport{
 		TLSClientConfig: &tls.Config{
 			InsecureSkipVerify: true,