diff --git a/cmake/Modules/EttercapLibCheck.cmake b/cmake/Modules/EttercapLibCheck.cmake
index 1c048c860..d0873a54c 100644
--- a/cmake/Modules/EttercapLibCheck.cmake
+++ b/cmake/Modules/EttercapLibCheck.cmake
@@ -332,5 +332,15 @@ if(ENABLE_LUA)
 endif()
 
 # Clean up
-list(REMOVE_DUPLICATES EC_INCLUDE)
-list(REMOVE_DUPLICATES EC_UI_INCLUDE)
+if(EC_INCLUDE)
+  list(REMOVE_DUPLICATES EC_INCLUDE)
+endif()
+if(EC_UI_INCLUDE)
+  list(REMOVE_DUPLICATES EC_UI_INCLUDE)
+endif()
+if(EC_LIBS)
+  list(REMOVE_DUPLICATES EC_LIBS)
+endif()
+if(EC_UI_LIBS)
+  list(REMOVE_DUPLICATES EC_UI_LIBS)
+endif()