diff --git a/packages/graph-node/src/loader.ts b/packages/graph-node/src/loader.ts
index 5eb038c8..dacbe2c6 100644
--- a/packages/graph-node/src/loader.ts
+++ b/packages/graph-node/src/loader.ts
@@ -778,9 +778,9 @@ export const instantiate = async (
       'json.toF64': async (decimal: number) => {
         return BigInt(__getString(decimal));
       },
-      // TODO: Debug toBigInt not working.
       'json.toBigInt': async (decimal: number) => {
-        return ASBigInt.fromString(decimal);
+        const ptr = await __newString(__getString(decimal));
+        return ASBigInt.fromString(ptr);
       }
     }
   };
diff --git a/packages/graph-node/test/subgraph/example1/src/mapping.ts b/packages/graph-node/test/subgraph/example1/src/mapping.ts
index 8f2f6c09..cc38c2f6 100644
--- a/packages/graph-node/test/subgraph/example1/src/mapping.ts
+++ b/packages/graph-node/test/subgraph/example1/src/mapping.ts
@@ -581,9 +581,9 @@ export function testJsonFromBytes (): void {
   // const i64Value = numberValue.toI64();
   // assert(i64Value == 123, 'values are not equal');
 
-  // TODO: Debug json toBigInt failing test case.
-  // const bigIntValue = numberValue.toBigInt();
-  // assert(bigIntValue.toString() == '123', 'values are not equal');
+  const bigIntValue = numberValue.toBigInt();
+  const expectedBigInt = BigInt.fromString('123');
+  assert(bigIntValue.equals(expectedBigInt), 'BigInt values are not equal');
 }
 
 export function testJsonTryFromBytes (): void {