diff --git a/src/main/java/com/google/api/generator/engine/ast/ClassDefinition.java b/src/main/java/com/google/api/generator/engine/ast/ClassDefinition.java
index 2a5fd9b685..40da0d793a 100644
--- a/src/main/java/com/google/api/generator/engine/ast/ClassDefinition.java
+++ b/src/main/java/com/google/api/generator/engine/ast/ClassDefinition.java
@@ -163,9 +163,10 @@ public ClassDefinition build() {
       }
 
       for (Statement statement : classDef.statements()) {
-        // TODO(xiaozhenliu): Add CommentStatement check here.
         Preconditions.checkState(
-            statement instanceof ExprStatement || statement instanceof BlockStatement,
+            statement instanceof ExprStatement
+                || statement instanceof BlockStatement
+                || statement instanceof CommentStatement,
             "Class statement type must be either an expression, block, or comment statement");
         if (statement instanceof ExprStatement) {
           Expr expr = ((ExprStatement) statement).expression();
diff --git a/src/test/java/com/google/api/generator/engine/ast/ClassDefinitionTest.java b/src/test/java/com/google/api/generator/engine/ast/ClassDefinitionTest.java
index b00da11d2a..d08ad60225 100644
--- a/src/test/java/com/google/api/generator/engine/ast/ClassDefinitionTest.java
+++ b/src/test/java/com/google/api/generator/engine/ast/ClassDefinitionTest.java
@@ -45,7 +45,7 @@ public void validClassDefinition_basicWithCommentsAndHeader() {
   }
 
   @Test
-  public void validClassDefinition_exprAndBlockStatements() {
+  public void validClassDefinition_exprCommentAndBlockStatements() {
     ClassDefinition.builder()
         .setName("LibraryServiceStub")
         .setIsNested(true)
@@ -53,6 +53,7 @@ public void validClassDefinition_exprAndBlockStatements() {
         .setStatements(
             Arrays.asList(
                 BlockStatement.builder().setIsStatic(true).build(),
+                CommentStatement.withComment(LineComment.withComment("Test line comment.")),
                 ExprStatement.withExpr(
                     AssignmentExpr.builder()
                         .setVariableExpr(