diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/logging/LoggingApplicationListener.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/logging/LoggingApplicationListener.java
index ac2854b9dd7..e9415ac11ae 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/logging/LoggingApplicationListener.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/logging/LoggingApplicationListener.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -320,12 +320,10 @@ public class LoggingApplicationListener implements GenericApplicationListener {
 	}
 
 	protected void initializeLogLevel(LoggingSystem system, LogLevel level) {
-		List<String> loggers = LOG_LEVEL_LOGGERS.get(level);
-		if (loggers != null) {
-			for (String logger : loggers) {
-				system.setLogLevel(logger, level);
-			}
-		}
+		LOG_LEVEL_LOGGERS.getOrDefault(level, Collections.emptyList()).stream()
+				.flatMap((logger) -> DEFAULT_GROUP_LOGGERS
+						.getOrDefault(logger, Collections.singletonList(logger)).stream())
+				.forEach((logger) -> system.setLogLevel(logger, level));
 	}
 
 	protected void setLogLevels(LoggingSystem system, Environment environment) {
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/logging/LoggingApplicationListenerTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/logging/LoggingApplicationListenerTests.java
index 8f5cafa3ac4..b0a4d711679 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/logging/LoggingApplicationListenerTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/logging/LoggingApplicationListenerTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -262,6 +262,18 @@ public class LoggingApplicationListenerTests {
 		assertThat(this.outputCapture.toString()).doesNotContain("testattrace");
 	}
 
+	@Test
+	public void parseDebugArgExpandGroups() {
+		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(this.context, "debug");
+		this.initializer.initialize(this.context.getEnvironment(),
+				this.context.getClassLoader());
+		this.logFactory.getInstance("org.springframework.boot.actuate.endpoint.web")
+				.debug("testdebugwebgroup");
+		this.logFactory.getInstance("org.hibernate.SQL").debug("testdebugsqlgroup");
+		assertThat(this.outputCapture.toString()).contains("testdebugwebgroup");
+		assertThat(this.outputCapture.toString()).contains("testdebugsqlgroup");
+	}
+
 	@Test
 	public void parseTraceArg() {
 		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(this.context, "trace");