diff --git a/CMakeLists.txt b/CMakeLists.txt
index 49ace2e0..3e265e57 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,7 +4,7 @@ project(psemek)
 set(CMAKE_CXX_STANDARD 17)
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
 
-string(TOUPPER ${CMAKE_BUILD_TYPE} PSEMEK_BUILD_TYPE)
+string(TOUPPER "${CMAKE_BUILD_TYPE}" PSEMEK_BUILD_TYPE)
 
 if(PSEMEK_BUILD_TYPE STREQUAL "DEBUG")
 	add_definitions("-DPSEMEK_DEBUG=1")