diff --git a/src/test/java/com/puppycrawl/tools/checkstyle/TreeWalkerTest.java b/src/test/java/com/puppycrawl/tools/checkstyle/TreeWalkerTest.java
index 1b43b179f..2652140d6 100644
--- a/src/test/java/com/puppycrawl/tools/checkstyle/TreeWalkerTest.java
+++ b/src/test/java/com/puppycrawl/tools/checkstyle/TreeWalkerTest.java
@@ -319,7 +319,7 @@ public class TreeWalkerTest extends BaseCheckTestSupport {
         }
     }
 
-    public static class BadJavaDocCheck extends Check {
+    private static class BadJavaDocCheck extends Check {
         @Override
         public int[] getDefaultTokens() {
             return getAcceptableTokens();
@@ -336,7 +336,7 @@ public class TreeWalkerTest extends BaseCheckTestSupport {
         }
     }
 
-    public static class RequiredTokenIsNotInDefaultsCheck extends Check {
+    private static class RequiredTokenIsNotInDefaultsCheck extends Check {
         @Override
         public int[] getRequiredTokens() {
             return new int[] {TokenTypes.ASSIGN};
@@ -353,7 +353,7 @@ public class TreeWalkerTest extends BaseCheckTestSupport {
         }
     }
 
-    public static class RequiredTokenIsEmptyIntArray extends Check {
+    private static class RequiredTokenIsEmptyIntArray extends Check {
         @Override
         public int[] getRequiredTokens() {
             return ArrayUtils.EMPTY_INT_ARRAY;