diff --git a/components/bootloader/subproject/CMakeLists.txt b/components/bootloader/subproject/CMakeLists.txt
index 09f261b492..f2df83fab9 100644
--- a/components/bootloader/subproject/CMakeLists.txt
+++ b/components/bootloader/subproject/CMakeLists.txt
@@ -37,7 +37,7 @@ set(COMPONENTS
 # Make EXTRA_COMPONENT_DIRS variable to point to the bootloader_components directory
 # of the project being compiled
 set(PROJECT_EXTRA_COMPONENTS "${PROJECT_SOURCE_DIR}/bootloader_components")
-set(EXTRA_COMPONENT_DIRS "${PROJECT_EXTRA_COMPONENTS}" APPEND)
+list(APPEND EXTRA_COMPONENT_DIRS "${PROJECT_EXTRA_COMPONENTS}")
 
 # Consider each directory in project's bootloader_components as a component to be compiled
 file(GLOB proj_components RELATIVE ${PROJECT_EXTRA_COMPONENTS} ${PROJECT_EXTRA_COMPONENTS}/*)