diff --git a/internal/ingress/annotations/authreq/main.go b/internal/ingress/annotations/authreq/main.go
index ad38c36b12..87278739f9 100644
--- a/internal/ingress/annotations/authreq/main.go
+++ b/internal/ingress/annotations/authreq/main.go
@@ -430,7 +430,7 @@ func (a authReq) Parse(ing *networking.Ingress) (interface{}, error) {
 		klog.V(3).InfoS("auth-set-proxy-headers annotation is undefined and will not be set", "err", err)
 	}
 
-	cns, _, err := cache.SplitMetaNamespaceKey(proxySetHeaderMap)
+	cns, cn, err := cache.SplitMetaNamespaceKey(proxySetHeaderMap)
 	if err != nil {
 		return nil, ing_errors.LocationDeniedError{
 			Reason: fmt.Errorf("error reading configmap name %s from annotation: %w", proxySetHeaderMap, err),
@@ -452,7 +452,7 @@ func (a authReq) Parse(ing *networking.Ingress) (interface{}, error) {
 	var proxySetHeaders map[string]string
 
 	if proxySetHeaderMap != "" {
-		proxySetHeadersMapContents, err := a.r.GetConfigMap(proxySetHeaderMap)
+		proxySetHeadersMapContents, err := a.r.GetConfigMap(cns + "/" + cn)
 		if err != nil {
 			return nil, ing_errors.NewLocationDenied(fmt.Sprintf("unable to find configMap %q", proxySetHeaderMap))
 		}
diff --git a/test/e2e/annotations/auth.go b/test/e2e/annotations/auth.go
index ddda1dce5f..f8aa8f5e95 100644
--- a/test/e2e/annotations/auth.go
+++ b/test/e2e/annotations/auth.go
@@ -329,6 +329,27 @@ var _ = framework.DescribeAnnotation("auth-*", func() {
 			})
 	})
 
+	ginkgo.It(`should set "proxy_set_header 'My-Custom-Header' '42';" when auth-headers are set without specified namespace`, func() {
+		host := authHost
+
+		annotations := map[string]string{
+			"nginx.ingress.kubernetes.io/auth-url":               "http://foo.bar/basic-auth/user/password",
+			"nginx.ingress.kubernetes.io/auth-proxy-set-headers": "auth-headers",
+		}
+
+		f.CreateConfigMap("auth-headers", map[string]string{
+			"My-Custom-Header": "42",
+		})
+
+		ing := framework.NewSingleIngress(host, "/", host, f.Namespace, framework.EchoService, 80, annotations)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return strings.Contains(server, `proxy_set_header 'My-Custom-Header' '42';`)
+			})
+	})
+
 	ginkgo.It(`should set cache_key when external auth cache is configured`, func() {
 		host := authHost