diff --git a/3rdparty/CMakeLists.txt b/3rdparty/CMakeLists.txt
index 48b4484..f1abd33 100644
--- a/3rdparty/CMakeLists.txt
+++ b/3rdparty/CMakeLists.txt
@@ -74,7 +74,7 @@ if (ENABLE_ZINT)
   if(PNG_FOUND)
     target_link_libraries(QZint PRIVATE PNG::PNG)
   else(PNG_FOUND)
-    target_compile_definitions(QZint -DNO_PNG)
+    target_compile_definitions(QZint PRIVATE -DNO_PNG)
   endif(PNG_FOUND)
 
 endif(ENABLE_ZINT)