diff --git a/clientconn.go b/clientconn.go
index 1e551a7041a..020cdae57e4 100644
--- a/clientconn.go
+++ b/clientconn.go
@@ -259,6 +259,8 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 		cc.authority = cc.dopts.authority
 	} else if strings.HasPrefix(cc.target, "unix:") {
 		cc.authority = "localhost"
+	} else if strings.HasPrefix(cc.parsedTarget.Endpoint, ":") {
+		cc.authority = "localhost" + cc.parsedTarget.Endpoint
 	} else {
 		// Use endpoint from "scheme://authority/endpoint" as the default
 		// authority for ClientConn.
diff --git a/test/authority_test.go b/test/authority_test.go
index 11c3c4c1af8..af289bc69ed 100644
--- a/test/authority_test.go
+++ b/test/authority_test.go
@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"net"
 	"os"
+	"sync"
 	"testing"
 	"time"
 
@@ -33,27 +34,31 @@ import (
 	testpb "google.golang.org/grpc/test/grpc_testing"
 )
 
+func authorityChecker(ctx context.Context, expectedAuthority string) (*testpb.Empty, error) {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return nil, status.Error(codes.InvalidArgument, "failed to parse metadata")
+	}
+	auths, ok := md[":authority"]
+	if !ok {
+		return nil, status.Error(codes.InvalidArgument, "no authority header")
+	}
+	if len(auths) != 1 {
+		return nil, status.Error(codes.InvalidArgument, fmt.Sprintf("no authority header, auths = %v", auths))
+	}
+	if auths[0] != expectedAuthority {
+		return nil, status.Error(codes.InvalidArgument, fmt.Sprintf("invalid authority header %v, expected %v", auths[0], expectedAuthority))
+	}
+	return &testpb.Empty{}, nil
+}
+
 func runUnixTest(t *testing.T, address, target, expectedAuthority string, dialer func(context.Context, string) (net.Conn, error)) {
 	if err := os.RemoveAll(address); err != nil {
 		t.Fatalf("Error removing socket file %v: %v\n", address, err)
 	}
-	us := &stubServer{
-		emptyCall: func(ctx context.Context, in *testpb.Empty) (*testpb.Empty, error) {
-			md, ok := metadata.FromIncomingContext(ctx)
-			if !ok {
-				return nil, status.Error(codes.InvalidArgument, "failed to parse metadata")
-			}
-			auths, ok := md[":authority"]
-			if !ok {
-				return nil, status.Error(codes.InvalidArgument, "no authority header")
-			}
-			if len(auths) < 1 {
-				return nil, status.Error(codes.InvalidArgument, "no authority header")
-			}
-			if auths[0] != expectedAuthority {
-				return nil, status.Error(codes.InvalidArgument, fmt.Sprintf("invalid authority header %v, expected %v", auths[0], expectedAuthority))
-			}
-			return &testpb.Empty{}, nil
+	ss := &stubServer{
+		emptyCall: func(ctx context.Context, _ *testpb.Empty) (*testpb.Empty, error) {
+			return authorityChecker(ctx, expectedAuthority)
 		},
 		network: "unix",
 		address: address,
@@ -63,14 +68,13 @@ func runUnixTest(t *testing.T, address, target, expectedAuthority string, dialer
 	if dialer != nil {
 		opts = append(opts, grpc.WithContextDialer(dialer))
 	}
-	if err := us.Start(nil, opts...); err != nil {
+	if err := ss.Start(nil, opts...); err != nil {
 		t.Fatalf("Error starting endpoint server: %v", err)
-		return
 	}
-	defer us.Stop()
-	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer ss.Stop()
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
-	_, err := us.client.EmptyCall(ctx, &testpb.Empty{})
+	_, err := ss.client.EmptyCall(ctx, &testpb.Empty{})
 	if err != nil {
 		t.Errorf("us.client.EmptyCall(_, _) = _, %v; want _, nil", err)
 	}
@@ -147,3 +151,40 @@ func (s) TestUnixCustomDialer(t *testing.T) {
 		})
 	}
 }
+
+func (s) TestColonPortAuthority(t *testing.T) {
+	expectedAuthority := ""
+	var authorityMu sync.Mutex
+	ss := &stubServer{
+		emptyCall: func(ctx context.Context, _ *testpb.Empty) (*testpb.Empty, error) {
+			authorityMu.Lock()
+			defer authorityMu.Unlock()
+			return authorityChecker(ctx, expectedAuthority)
+		},
+		network: "tcp",
+	}
+	if err := ss.Start(nil); err != nil {
+		t.Fatalf("Error starting endpoint server: %v", err)
+	}
+	defer ss.Stop()
+	_, port, err := net.SplitHostPort(ss.address)
+	if err != nil {
+		t.Fatalf("Failed splitting host from post: %v", err)
+	}
+	authorityMu.Lock()
+	expectedAuthority = "localhost:" + port
+	authorityMu.Unlock()
+	// ss.Start dials, but not the ":[port]" target that is being tested here.
+	// Dial again, with ":[port]" as the target.
+	cc, err := grpc.Dial(":"+port, grpc.WithInsecure())
+	if err != nil {
+		t.Fatalf("grpc.Dial(%q) = %v", ss.target, err)
+	}
+	defer cc.Close()
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	_, err = testpb.NewTestServiceClient(cc).EmptyCall(ctx, &testpb.Empty{})
+	if err != nil {
+		t.Errorf("us.client.EmptyCall(_, _) = _, %v; want _, nil", err)
+	}
+}