diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4689566..e3475f7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -265,6 +265,7 @@ if(UNIX AND NOT APPLE)
   if(X11_Xcursor_FOUND)
     set(FLTK_LIBRARIES ${FLTK_LIBRARIES} ${X11_Xcursor_LIB})
   endif()
+  set(FLTK_LIBRARIES ${FLTK_LIBRARIES} png)
 endif()
 
 if(FLTK_FOUND)