diff --git a/packages/inter-protocol/jsconfig.build.json b/packages/inter-protocol/jsconfig.build.json
new file mode 100644
index 00000000000..b674676c8fe
--- /dev/null
+++ b/packages/inter-protocol/jsconfig.build.json
@@ -0,0 +1,6 @@
+{
+    "extends": [
+        "./jsconfig.json",
+        "../../tsconfig-build-options.json"
+    ]
+}
diff --git a/packages/inter-protocol/package.json b/packages/inter-protocol/package.json
index d701ee4a308..77127790d8f 100644
--- a/packages/inter-protocol/package.json
+++ b/packages/inter-protocol/package.json
@@ -11,6 +11,8 @@
     "build": "yarn build:bundles",
     "build:bundles": "node ./scripts/build-bundles.js",
     "build:add-STARS-proposal": "agoric run scripts/add-STARS.js",
+    "prepack": "tsc --build jsconfig.build.json",
+    "postpack": "git clean -f '*.d.ts*' src/types.js",
     "test": "ava",
     "test:c8": "c8 $C8_OPTIONS ava --config=ava-nesm.config.js",
     "test:xs": "exit 0",
diff --git a/packages/inter-protocol/src/proposals/startPSM.js b/packages/inter-protocol/src/proposals/startPSM.js
index 8a0f871788c..d5cd008609d 100644
--- a/packages/inter-protocol/src/proposals/startPSM.js
+++ b/packages/inter-protocol/src/proposals/startPSM.js
@@ -345,13 +345,14 @@ export const makeAnchorAsset = async (
     }),
   );
 
-  /** @type {{ creatorFacet: ERef<Mint<'nat'>>, publicFacet: ERef<Issuer<'nat'>> }} */
-  // @ts-expect-error cast
-  const { creatorFacet: mint, publicFacet: issuer } = await E(startUpgradable)({
-    installation: mintHolder,
-    label: keyword,
-    terms,
-  });
+  const { creatorFacet: mint, publicFacet: issuer } =
+    /** @type {{ creatorFacet: ERef<Mint<'nat'>>, publicFacet: ERef<Issuer<'nat'>> }} */ (
+      await E(startUpgradable)({
+        installation: mintHolder,
+        label: keyword,
+        terms,
+      })
+    );
 
   const brand = await E(issuer).getBrand();
   const kit = harden({ mint, issuer, brand });