diff --git a/test/testpaint/Printer.cpp b/test/testpaint/Printer.cpp
index 77915fc4b2..03966d128c 100644
--- a/test/testpaint/Printer.cpp
+++ b/test/testpaint/Printer.cpp
@@ -157,7 +157,7 @@ namespace Printer {
         s += "\n";
 
         for (int direction = 0; direction < 4; ++direction) {
-            printf("  +           +  ");
+            s += "  +           +  ";
         }
         s += "\n";