diff --git a/implementations/javascript/packages/schema/src/checker.ts b/implementations/javascript/packages/schema/src/checker.ts
index 8e8b118..f9a4043 100644
--- a/implementations/javascript/packages/schema/src/checker.ts
+++ b/implementations/javascript/packages/schema/src/checker.ts
@@ -2,14 +2,16 @@ import { typeFor, typeForIntersection } from './gentype';
 import { ANY_TYPE, SimpleType } from './type';
 import * as M from './meta';
 
-export function checkSchema(schema: M.Schema): M.Schema {
+export function checkSchema(schema: M.Schema): (
+    { ok: true, schema: M.Schema } | { ok: false, problems: Array<string> })
+{
     const checker = new Checker();
     schema.definitions.forEach(checker.checkDefinition.bind(checker));
     if (checker.problems.length > 0) {
-        throw new Error(`Schema does not specify a bijection:\n` +
-            checker.problems.map(c => ' - ' + c).join('\n'));
+        return { ok: false, problems: checker.problems };
+    } else {
+        return { ok: true, schema };
     }
-    return schema;
 }
 
 class Checker {
diff --git a/implementations/javascript/packages/schema/src/reader.ts b/implementations/javascript/packages/schema/src/reader.ts
index 5f90ee6..36f44e3 100644
--- a/implementations/javascript/packages/schema/src/reader.ts
+++ b/implementations/javascript/packages/schema/src/reader.ts
@@ -59,7 +59,10 @@ function _readSchema(source: string, options?: ReaderOptions<never>): Array<Inpu
 export function readSchema(source: string,
                            options?: ReaderOptions<never> & SchemaReaderOptions): Schema
 {
-    return checkSchema(parseSchema(_readSchema(source, options), options ?? {}));
+    const checked = checkSchema(parseSchema(_readSchema(source, options), options ?? {}));
+    if (checked.ok) return checked.schema;
+    throw new Error(`Schema does not specify a bijection:\n` +
+        checked.problems.map(c => ' - ' + c).join('\n'));
 }
 
 export function parseSchema(toplevelTokens: Array<Input>,