diff --git a/vendor/google.golang.org/grpc/service_config.go b/vendor/google.golang.org/grpc/service_config.go
index d0787f1..686ad7b 100644
--- a/vendor/google.golang.org/grpc/service_config.go
+++ b/vendor/google.golang.org/grpc/service_config.go
@@ -310,6 +310,14 @@
 			}
 			break
 		}
+		if sc.lbConfig == nil {
+			// We had a loadBalancingConfig field but did not encounter a
+			// supported policy.  The config is considered invalid in this
+			// case.
+			err := fmt.Errorf("invalid loadBalancingConfig: no supported policies found")
+			grpclog.Warningf(err.Error())
+			return nil, err
+		}
 	}
 
 	if rsc.MethodConfig == nil {