diff --git a/README.md b/README.md
index 5756e64..a594d0d 100644
--- a/README.md
+++ b/README.md
@@ -586,6 +586,12 @@ and `#extension` have no effect, and can be fully preserved as part of parsing.
 
 ## Deviations from the Khronos Grammar
 
+- The parser allows for programs to contain top level preprocessor statements,
+  like `#define X`, as a convenience to avoid preprocessing some programs, and
+  for simple programs lets you preserve preprocessor lines in the AST if you
+  want to do something specific with them. However, preprocessor statements at
+  any other part of the program are not allowed. The Khronos grammar does not
+  include preprocessor statements.
 - `selection_statement` is renamed to `if_statement`
 - The grammar specifies `declaration` itself ends with a semicolon. I moved the
   semicolon into the `declaration_statement` rule.
diff --git a/package.json b/package.json
index 04fa0b2..04fc230 100644
--- a/package.json
+++ b/package.json
@@ -3,7 +3,7 @@
   "engines": {
     "node": ">=16"
   },
-  "version": "5.2.0",
+  "version": "5.3.0",
   "type": "module",
   "description": "A GLSL ES 1.0 and 3.0 parser and preprocessor that can preserve whitespace and comments",
   "scripts": {
diff --git a/src/ast/ast-types.ts b/src/ast/ast-types.ts
index fa96064..78e7bfa 100644
--- a/src/ast/ast-types.ts
+++ b/src/ast/ast-types.ts
@@ -6,10 +6,16 @@
 
 import { Scope } from '../parser/scope.js';
 
+// Valid top level program lines
+export type ProgramStatement =
+  | PreprocessorNode
+  | DeclarationStatementNode
+  | FunctionNode;
+
 // The overall result of parsing, which incldues the AST and scopes
 export interface Program {
   type: 'program';
-  program: (PreprocessorNode | DeclarationStatementNode | FunctionNode)[];
+  program: ProgramStatement[];
   scopes: Scope[];
   wsStart?: string;
   wsEnd?: string;