diff --git a/internal/lsp/diagnostics.go b/internal/lsp/diagnostics.go
index acf3820..f9e1a47 100644
--- a/internal/lsp/diagnostics.go
+++ b/internal/lsp/diagnostics.go
@@ -439,6 +439,10 @@
 	if err != nil {
 		return nil
 	}
+	// If the file no longer has a name ending in .go, this diagnostic is wrong
+	if filepath.Ext(fh.URI().Filename()) != ".go" {
+		return nil
+	}
 	// TODO(rstambler): We should be able to parse the build tags in the
 	// file and show a more specific error message. For now, put the diagnostic
 	// on the package declaration.