diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index f70eb8dc187..0a8825990a4 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -193,8 +193,14 @@ function(find_dependent_plugins varName)
 endfunction()
 
 function(qtc_plugin_enabled varName name)
-  string(TOUPPER "BUILD_PLUGIN_${name}" _build_plugin_var)
-  set(${varName} ${${_build_plugin_var}} PARENT_SCOPE)
+  if (NOT (name IN_LIST __QTC_PLUGINS))
+    message(FATAL_ERROR "extend_qtc_plugin: Unknown plugin target \"${name}\"")
+  endif()
+  if (TARGET ${name})
+    set(${varName} ON PARENT_SCOPE)
+  else()
+    set(${varName} OFF PARENT_SCOPE)
+  endif()
 endfunction()
 
 function(add_qtc_plugin target_name)