diff --git a/CMakeLists.txt b/CMakeLists.txt
index 88af909..6f84b30 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -247,23 +247,15 @@
   # No proper handling for extra X11 libs that FLTK might need...
   if(X11_Xft_FOUND)
     set(FLTK_LIBRARIES ${FLTK_LIBRARIES} ${X11_Xft_LIB})
-  else()
-    message(FATAL_ERROR "Xft headers/libraries not found (needed by FLTK.)")
   endif()
   if(X11_Xinerama_FOUND)
     set(FLTK_LIBRARIES ${FLTK_LIBRARIES} ${X11_Xinerama_LIB})
-  else()
-    message(FATAL_ERROR "Xinerama headers/libraries not found (needed by FLTK.)")
   endif()
   if(X11_Xfixes_FOUND)
     set(FLTK_LIBRARIES ${FLTK_LIBRARIES} ${X11_Xfixes_LIB})
-  else()
-    message(FATAL_ERROR "Xfixes headers/libraries not found (needed by FLTK.)")
   endif()
   if(X11_Xcursor_FOUND)
     set(FLTK_LIBRARIES ${FLTK_LIBRARIES} ${X11_Xcursor_LIB})
-  else()
-    message(FATAL_ERROR "Xcursor headers/libraries not found (needed by FLTK.)")
   endif()
 endif()
 
@@ -298,6 +290,22 @@
   set(USE_INCLUDED_FLTK 1)
 endif()
 if(USE_INCLUDED_FLTK)
+  # Check that we have the proper dependencies
+  if(UNIX AND NOT APPLE)
+    if(NOT X11_Xft_FOUND)
+      message(FATAL_ERROR "Xft headers/libraries not found (needed by FLTK.)")
+    endif()
+    if(NOT X11_Xinerama_FOUND)
+      message(FATAL_ERROR "Xinerama headers/libraries not found (needed by FLTK.)")
+    endif()
+    if(NOT X11_Xfixes_FOUND)
+      message(FATAL_ERROR "Xfixes headers/libraries not found (needed by FLTK.)")
+    endif()
+    if(NOT X11_Xcursor_FOUND)
+      message(FATAL_ERROR "Xcursor headers/libraries not found (needed by FLTK.)")
+    endif()
+  endif()
+
   set(HAVE_FLTK_DEAD_KEYS 1)
   set(HAVE_FLTK_CLIPBOARD 1)
   set(HAVE_FLTK_MEDIAKEYS 1)