diff --git a/sched/sched/CMakeLists.txt b/sched/sched/CMakeLists.txt
index 1f7d29875bb..782234f846d 100644
--- a/sched/sched/CMakeLists.txt
+++ b/sched/sched/CMakeLists.txt
@@ -48,8 +48,7 @@ set(SRCS
     sched_sysinfo.c
     sched_get_stateinfo.c
     sched_switchcontext.c
-    sched_sleep.c
-    sched_processtimer.c)
+    sched_sleep.c)
 
 if(DEFINED CONFIG_STACKCHECK_MARGIN)
   if(NOT CONFIG_STACKCHECK_MARGIN EQUAL -1)
@@ -99,6 +98,8 @@ endif()
 
 if(CONFIG_SCHED_TICKLESS)
   list(APPEND SRCS sched_timerexpiration.c)
+else()
+  list(APPEND SRCS sched_processtimer.c)
 endif()
 
 if(CONFIG_SCHED_CRITMONITOR)
diff --git a/sched/sched/Make.defs b/sched/sched/Make.defs
index 232408a7536..71a7bc2ce6b 100644
--- a/sched/sched/Make.defs
+++ b/sched/sched/Make.defs
@@ -30,7 +30,7 @@ CSRCS += sched_yield.c sched_rrgetinterval.c sched_foreach.c
 CSRCS += sched_lock.c sched_unlock.c sched_lockcount.c
 CSRCS += sched_idletask.c sched_self.c sched_get_stackinfo.c sched_get_tls.c
 CSRCS += sched_sysinfo.c sched_get_stateinfo.c sched_getcpu.c
-CSRCS += sched_switchcontext.c sched_sleep.c sched_processtimer.c
+CSRCS += sched_switchcontext.c sched_sleep.c
 
 ifneq ($(CONFIG_STACKCHECK_MARGIN),)
   ifneq ($(CONFIG_STACKCHECK_MARGIN),-1)
@@ -80,6 +80,8 @@ endif
 
 ifeq ($(CONFIG_SCHED_TICKLESS),y)
 CSRCS += sched_timerexpiration.c
+else
+CSRCS += sched_processtimer.c
 endif
 
 ifeq ($(CONFIG_SCHED_CRITMONITOR),y)