diff --git a/.changeset/blue-insects-visit.md b/.changeset/blue-insects-visit.md
new file mode 100644
index 000000000..70092a2ef
--- /dev/null
+++ b/.changeset/blue-insects-visit.md
@@ -0,0 +1,5 @@
+---
+'@graphprotocol/graph-cli': patch
+---
+
+fix bug with duplicate IDs - #1604
diff --git a/packages/cli/src/protocols/ethereum/codegen/abi.ts b/packages/cli/src/protocols/ethereum/codegen/abi.ts
index 46fa09d77..0773f74a1 100644
--- a/packages/cli/src/protocols/ethereum/codegen/abi.ts
+++ b/packages/cli/src/protocols/ethereum/codegen/abi.ts
@@ -358,7 +358,8 @@ export default class AbiCodeGenerator {
     }
 
     const tupleIdentifier = parentClass + tsCodegen.namedType(name).capitalize();
-    const tupleClassName = tupleIdentifier + 'Struct';
+    const tupleClassName =
+      tupleIdentifier + (parentField === 'outputValues' ? 'Output' : '') + 'Struct';
     let tupleClasses: any[] = [];
 
     const isTupleType = util.isTupleType(type);