diff --git a/logging/zap/grpclogger.go b/logging/zap/grpclogger.go
index 9d5ac5f77..daf463c3d 100644
--- a/logging/zap/grpclogger.go
+++ b/logging/zap/grpclogger.go
@@ -133,5 +133,7 @@ func (l *zapGrpcLoggerV2) Fatalf(format string, args ...interface{}) {
 }
 
 func (l *zapGrpcLoggerV2) V(level int) bool {
-	return l.verbosity <= level
+	// Check whether the verbosity of the current log ('level') is within the specified threshold ('l.verbosity').
+	// As in https://github.com/grpc/grpc-go/blob/41e044e1c82fcf6a5801d6cbd7ecf952505eecb1/grpclog/loggerv2.go#L199-L201.
+	return level <= l.verbosity
 }
diff --git a/logging/zap/grpclogger_test.go b/logging/zap/grpclogger_test.go
index 38b3ec11d..86d3aa613 100644
--- a/logging/zap/grpclogger_test.go
+++ b/logging/zap/grpclogger_test.go
@@ -14,25 +14,26 @@ import (
 )
 
 func Test_zapGrpcLogger_V(t *testing.T) {
-	// copied from gRPC
 	const (
-		// infoLog indicates Info severity.
-		infoLog int = iota
-		// warningLog indicates Warning severity.
-		warningLog
-		// errorLog indicates Error severity.
-		errorLog
-		// fatalLog indicates Fatal severity.
-		fatalLog
+		// The default verbosity level.
+		// See https://github.com/grpc/grpc-go/blob/8ab16ef276a33df4cdb106446eeff40ff56a6928/grpclog/loggerv2.go#L108.
+		normal = 0
+
+		// Currently the only level of "being verbose".
+		// For example https://github.com/grpc/grpc-go/blob/8ab16ef276a33df4cdb106446eeff40ff56a6928/grpclog/grpclog.go#L21.
+		verbose = 2
+
+		// As is mentioned in https://github.com/grpc/grpc-go/blob/8ab16ef276a33df4cdb106446eeff40ff56a6928/README.md#how-to-turn-on-logging,
+		// though currently not being used in the code.
+		extremelyVerbose = 99
 	)
 
 	core, _ := observer.New(zapcore.DebugLevel)
 	logger := zap.New(core)
-	ReplaceGrpcLoggerV2WithVerbosity(logger, warningLog)
-	assert.False(t, grpclog.V(infoLog))
-	assert.True(t, grpclog.V(warningLog))
-	assert.True(t, grpclog.V(errorLog))
-	assert.True(t, grpclog.V(fatalLog))
+	ReplaceGrpcLoggerV2WithVerbosity(logger, verbose)
+	assert.True(t, grpclog.V(normal))
+	assert.True(t, grpclog.V(verbose))
+	assert.False(t, grpclog.V(extremelyVerbose))
 }
 
 func TestReplaceGrpcLoggerV2(t *testing.T) {