diff --git a/js/data.go b/js/data.go
index b9d7812e..42afaee4 100644
--- a/js/data.go
+++ b/js/data.go
@@ -63,7 +63,7 @@ func gzipCompress(call otto.FunctionCall) otto.Value {
 
 	arg := argv[0]
 	if (!arg.IsString()) {
-		return ReportError("btoa: single argument must be a string.")
+		return ReportError("gzipCompress: single argument must be a string.")
 	}
 
 	uncompressedBytes := []byte(arg.String())