diff --git a/checkstyle.xml b/checkstyle.xml
index 72e6d0ba8b..7ca92c844d 100644
--- a/checkstyle.xml
+++ b/checkstyle.xml
@@ -6,6 +6,12 @@
 		<module name="LeftCurly">
 			<property name="option" value="nl"/>
 		</module>
+		<!-- require tabs for indenting - https://stackoverflow.com/a/28550141 -->
+		<module name="RegexpSinglelineJava">
+			<property name="format" value="^\t* "/>
+			<property name="message" value="Indent must use tab characters"/>
+			<property name="ignoreComments" value="true"/>
+		</module>
 	</module>
 	<module name="SuppressionFilter">
 		<property name="file" value="suppressions.xml"/>
diff --git a/runelite-api/src/main/java/net/runelite/api/GameState.java b/runelite-api/src/main/java/net/runelite/api/GameState.java
index e91f1d3a6b..cb7e70fbde 100644
--- a/runelite-api/src/main/java/net/runelite/api/GameState.java
+++ b/runelite-api/src/main/java/net/runelite/api/GameState.java
@@ -22,31 +22,34 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
-
 package net.runelite.api;
 
 public enum GameState
 {
-   UNKNOWN(-1),
-   STARTING(0),
-   LOGIN_SCREEN(10),
-   LOGGING_IN(20),
-   LOADING(25),
-   LOGGED_IN(30),
-   HOPPING(45);
+	UNKNOWN(-1),
+	STARTING(0),
+	LOGIN_SCREEN(10),
+	LOGGING_IN(20),
+	LOADING(25),
+	LOGGED_IN(30),
+	HOPPING(45);
 
-   private final int state;
+	private final int state;
 
-   GameState(int state)
-   {
-	   this.state = state;
-   }
+	GameState(int state)
+	{
+		this.state = state;
+	}
 
-   public static GameState of(int state)
-   {
-	   for (GameState gs : GameState.values())
-		   if (gs.state == state)
-			   return gs;
-	   return UNKNOWN;
-   }
+	public static GameState of(int state)
+	{
+		for (GameState gs : GameState.values())
+		{
+			if (gs.state == state)
+			{
+				return gs;
+			}
+		}
+		return UNKNOWN;
+	}
 }