diff --git a/airspec/src/main/scala/wvlet/airspec/runner/AirSpecSbtRunner.scala b/airspec/src/main/scala/wvlet/airspec/runner/AirSpecSbtRunner.scala
index 6697c9aeb..061c05133 100644
--- a/airspec/src/main/scala/wvlet/airspec/runner/AirSpecSbtRunner.scala
+++ b/airspec/src/main/scala/wvlet/airspec/runner/AirSpecSbtRunner.scala
@@ -81,25 +81,40 @@ private[airspec] object AirSpecSbtRunner extends LogSupport {
       var i                   = 0
       var logLevel: LogLevel  = Logger.getDefaultLogLevel
       val additionalLogLevels = Map.newBuilder[String, LogLevel]
+
+      def parseAdditionalLogLevel(s: String): Unit = {
+        s.split("=") match {
+          case Array(pkg, level) =>
+            additionalLogLevels += pkg -> LogLevel(level)
+          case _ =>
+            warn(s"Ignoring invalid argument: ${s}. Use -L (package)=(log level) to set log levels")
+        }
+      }
+
+      var warnings: Set[String] = Set.empty
+
       while (i < args.length) {
         args(i) match {
           case "-l" if i < args.length - 1 =>
             // Set the default log level for the test spec
             logLevel = LogLevel(args(i + 1))
             i += 1
+          case "-L" if i < args.length - 1 =>
+            parseAdditionalLogLevel(args(i + 1))
+            i += 1
           case arg if arg.startsWith("-L") =>
-            arg.stripPrefix("-L").split("=") match {
-              case Array(pkg, level) =>
-                additionalLogLevels += pkg -> LogLevel(level)
-              case _ =>
-                warn(s"Ignoring invalid argument: ${arg}. Use -L(package)=(log level) to set log levels")
-            }
+            warnings += s"-L(package)=(log level) syntax is deprecated. Use -L (package)=(log level)"
+            parseAdditionalLogLevel(arg.stripPrefix("-L"))
           case other =>
             remaining += other
         }
         i += 1
       }
 
+      if (warnings.nonEmpty) {
+        warn(warnings.mkString("\n"))
+      }
+
       remainingArgs = remaining.result()
       _defaultLogLevel = logLevel
       _additionalLogLevels = additionalLogLevels.result()
diff --git a/docs/airspec.md b/docs/airspec.md
index 5e50e7d2a..53a44b7c7 100644
--- a/docs/airspec.md
+++ b/docs/airspec.md
@@ -173,7 +173,7 @@ $ sbt
 
 # Configure log levels of airframe-log
 > testOnly -- -l (level)                 # Set the log level for the test target classes
-> testOnly -- -L(package)=(level)        # Set log level for a specific package or class
+> testOnly -- -L (package)=(level)       # Set log level for a specific package or class
 
 # sbt's default test functionalities:
 > testQuick                              # Run only previously failed test specs
@@ -257,17 +257,17 @@ AirSpec natively supports [airframe-log](https://wvlet.org/airframe/docs/airfram
 This will set the log level to debug for all test classes.
 
 
-To change the log level only for a specific package or a class, use `-L(package or class)=(log level)` option:
+To change the log level only for a specific package or a class, use `-L (package or class)=(log level)` option:
 
 ```scala
-> testOnly -- -Lorg.mydomain.myapp=debug
+> testOnly -- -L org.mydomain.myapp=debug
 ```
 You can use multiple `-L` options to set different log levels for multiple packages.
 
 You can also use wildcard `*` with `-L` option for the ease of setting log levels for specific classes:
 ```scala
-> testOnly -- -Lmyapp.*=debug
-> testOnly -- -L*.MyClass=debug
+> testOnly -- -L myapp.*=debug
+> testOnly -- -L *.MyClass=debug
 ```
 
 ### Configure Log Levels in log-test.properties