diff --git a/src/playground-project.ts b/src/playground-project.ts
index 7db395a4..f64a6e02 100644
--- a/src/playground-project.ts
+++ b/src/playground-project.ts
@@ -784,7 +784,7 @@ const validateImportMap = (importMap: unknown): string[] => {
       );
     }
     try {
-      new URL(resolutionResult);
+      new URL(resolutionResult, import.meta.url);
     } catch {
       errors.push(
         `Import map key "${specifierKey}" is invalid because` +