diff --git a/CMakeLists.txt b/CMakeLists.txt
index a9e82b335..17624eb88 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -67,7 +67,7 @@ endif()
 # add project code
 add_subdirectory(src)
 
-if(!${projectPrefix}API_FREESTANDING)
+if(NOT ${projectPrefix}API_FREESTANDING)
     # add usage example
     add_subdirectory(example)
 endif()
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 5519a7df3..cdc5120da 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -22,7 +22,7 @@
 
 cmake_minimum_required(VERSION 3.5)
 
-if(!${projectPrefix}API_FREESTANDING)
+if(NOT ${projectPrefix}API_FREESTANDING)
     add_subdirectory(runtime)
 endif()
 add_subdirectory(static)