diff --git a/packages/babylon/ast/spec.md b/packages/babylon/ast/spec.md
index 0764d979f1..71b992fbcf 100644
--- a/packages/babylon/ast/spec.md
+++ b/packages/babylon/ast/spec.md
@@ -1212,7 +1212,7 @@ interface OptFunctionDeclaration <: FunctionDeclaration {
   id: Identifier | null;
 }
 
-interface OptClasDeclaration <: ClassDeclaration {
+interface OptClassDeclaration <: ClassDeclaration {
   id: Identifier | null;
 }