diff --git a/share/sysbuild/cmake/modules/sysbuild_kconfig.cmake b/share/sysbuild/cmake/modules/sysbuild_kconfig.cmake
index 23932d4494..d18b5b7978 100644
--- a/share/sysbuild/cmake/modules/sysbuild_kconfig.cmake
+++ b/share/sysbuild/cmake/modules/sysbuild_kconfig.cmake
@@ -17,11 +17,9 @@ if(DEFINED SB_CONF_FILE)
   # SB_CONF_FILE already set so nothing to do.
 elseif(DEFINED ENV{SB_CONF_FILE})
   set(SB_CONF_FILE $ENV{SB_CONF_FILE})
-elseif(EXISTS      ${APP_DIR}/sysbuild.conf)
-  set(SB_CONF_FILE ${APP_DIR}/sysbuild.conf)
 else()
-  # Because SYSBuild is opt-in feature, then it is permitted to not have a
-  # SYSBuild dedicated configuration file.
+  # sysbuild.conf is an optional file, because sysbuild is an opt-in feature.
+  zephyr_file(CONF_FILES ${APP_DIR} KCONF SB_CONF_FILE NAMES "sysbuild.conf" SUFFIX ${FILE_SUFFIX})
 endif()
 
 if(NOT DEFINED SB_EXTRA_CONF_FILE AND DEFINED SB_OVERLAY_CONFIG)