diff --git a/internal/dag/httpproxy_processor.go b/internal/dag/httpproxy_processor.go
index a0ede5f154a..377132d928e 100644
--- a/internal/dag/httpproxy_processor.go
+++ b/internal/dag/httpproxy_processor.go
@@ -705,7 +705,8 @@ func (p *HTTPProxyProcessor) validHTTPProxies() []*contour_api_v1.HTTPProxy {
 			valid = append(valid, proxy)
 			continue
 		}
-		fqdnHTTPProxies[proxy.Spec.VirtualHost.Fqdn] = append(fqdnHTTPProxies[proxy.Spec.VirtualHost.Fqdn], proxy)
+		fqdn := strings.ToLower(proxy.Spec.VirtualHost.Fqdn)
+		fqdnHTTPProxies[fqdn] = append(fqdnHTTPProxies[fqdn], proxy)
 	}
 
 	for fqdn, proxies := range fqdnHTTPProxies {
diff --git a/internal/dag/status_test.go b/internal/dag/status_test.go
index 91dde118dcd..5dc7ceac86d 100644
--- a/internal/dag/status_test.go
+++ b/internal/dag/status_test.go
@@ -810,6 +810,24 @@ func TestDAGStatus(t *testing.T) {
 		},
 	}
 
+	proxyValidReuseCaseExampleCom := &contour_api_v1.HTTPProxy{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "case-example",
+			Namespace: "roots",
+		},
+		Spec: contour_api_v1.HTTPProxySpec{
+			VirtualHost: &contour_api_v1.VirtualHost{
+				Fqdn: "EXAMPLE.com",
+			},
+			Routes: []contour_api_v1.Route{{
+				Services: []contour_api_v1.Service{{
+					Name: "kuard",
+					Port: 8080,
+				}},
+			}},
+		},
+	}
+
 	run(t, "conflicting proxies due to fqdn reuse", testcase{
 		objs: []interface{}{proxyValidExampleCom, proxyValidReuseExampleCom},
 		want: map[types.NamespacedName]contour_api_v1.DetailedCondition{
@@ -822,6 +840,18 @@ func TestDAGStatus(t *testing.T) {
 		},
 	})
 
+	run(t, "conflicting proxies due to fqdn reuse with uppercase/lowercase", testcase{
+		objs: []interface{}{proxyValidExampleCom, proxyValidReuseCaseExampleCom},
+		want: map[types.NamespacedName]contour_api_v1.DetailedCondition{
+			{Name: proxyValidExampleCom.Name, Namespace: proxyValidExampleCom.Namespace}: fixture.NewValidCondition().
+				WithGeneration(proxyValidExampleCom.Generation).
+				WithError(contour_api_v1.ConditionTypeVirtualHostError, "DuplicateVhost", `fqdn "example.com" is used in multiple HTTPProxies: roots/case-example, roots/example-com`),
+			{Name: proxyValidReuseCaseExampleCom.Name, Namespace: proxyValidReuseCaseExampleCom.Namespace}: fixture.NewValidCondition().
+				WithGeneration(proxyValidReuseCaseExampleCom.Generation).
+				WithError(contour_api_v1.ConditionTypeVirtualHostError, "DuplicateVhost", `fqdn "example.com" is used in multiple HTTPProxies: roots/case-example, roots/example-com`),
+		},
+	})
+
 	proxyRootIncludesRoot := &contour_api_v1.HTTPProxy{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:      "root-blog",