diff --git a/buildfiles/run.go b/buildfiles/run.go
index ffb3499b..e412c03c 100644
--- a/buildfiles/run.go
+++ b/buildfiles/run.go
@@ -103,7 +103,7 @@ func (e *runContext) runBuildFilesForPackage(pkg *packages.Package, bc *breadcru
 		return nil
 	}
 
-	pkg.Globals = starlark.StringDict{}
+	pkgGlobals := starlark.StringDict{}
 	for _, file := range pkg.SourceFiles {
 		globals, err := e.RunBuildFile(pkg, file, nbc)
 		if err != nil {
@@ -111,10 +111,12 @@ func (e *runContext) runBuildFilesForPackage(pkg *packages.Package, bc *breadcru
 		}
 
 		for k, v := range globals {
-			pkg.Globals[k] = v
+			pkgGlobals[k] = v
 		}
 	}
 
+	pkg.Globals = pkgGlobals
+
 	return nil
 }