diff --git a/CMakeLists.txt b/CMakeLists.txt
index b5ae0435055b..1d1d8d585ae4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -235,12 +235,12 @@ file(GLOB SOURCES
 )
 
 add_executable(lightgbm src/main.cpp ${SOURCES})
-set(SOURCES "${SOURCES} src/c_api.cpp")
+list(APPEND SOURCES "src/c_api.cpp")
 
 # Only build the R part of the library if building for
 # use with the R package
 if(BUILD_FOR_R)
-  set(SOURCES "${SOURCES} src/lightgbm_R.cpp")
+  list(APPEND SOURCES "src/lightgbm_R.cpp")
 endif(BUILD_FOR_R)
 
 add_library(_lightgbm SHARED ${SOURCES})