diff --git a/packages/shared-internals/src/package-cache.ts b/packages/shared-internals/src/package-cache.ts
index 6e1c467a8..cd4767273 100644
--- a/packages/shared-internals/src/package-cache.ts
+++ b/packages/shared-internals/src/package-cache.ts
@@ -67,6 +67,12 @@ export default class PackageCache {
   }
 
   ownerOfFile(filename: string): Package | undefined {
+    // this can arise if anyone is using @embroider/macros with babel on an explicit
+    // string (not a file on disk). We should never even try to check owner of the
+    // file since there is no file that can be owned
+    if (!filename) {
+      return undefined;
+    }
     let candidate = filename;
     const virtualPrefix = 'embroider_virtual:';
 
diff --git a/packages/shared-internals/src/paths.ts b/packages/shared-internals/src/paths.ts
index f6cea73b0..632b5c584 100644
--- a/packages/shared-internals/src/paths.ts
+++ b/packages/shared-internals/src/paths.ts
@@ -48,6 +48,12 @@ const postfixRE = /[?#].*$/s;
 // cache-busting query params from leaking where they shouldn't.
 // includeHashSign true means #my-specifier is considered part of the pathname
 export function cleanUrl(url: string): string {
+  // a tiny bit of defensive programming to make sure that things won't explode
+  // a simple example is executing babel with @embroider/macros on a file without
+  // a filename (not on disk) will cause an error here
+  if (!url) {
+    return url;
+  }
   const regexp = postfixRE;
   return url.replace(regexp, '');
 }