diff --git a/CMakeLists.txt b/CMakeLists.txt
index 46f6a4a..a668fed 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,7 +3,7 @@ project(si4010prog C)
 
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 
-set(CMAKE_C_FLAGS ${CMAKE_C_FLAGS} -Wall)
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall")
 
 # Build Options
 option(WITH_C2_BUS_FT232 "Enable FTDI FT232 based C2 Bus interface" OFF)