diff --git a/include/sys_clock.h b/include/sys_clock.h
index 287d1c77c34..0f485a77118 100644
--- a/include/sys_clock.h
+++ b/include/sys_clock.h
@@ -79,27 +79,20 @@ static inline int sys_clock_hw_cycles_per_tick(void)
 
 /* kernel clocks */
 
-#ifdef CONFIG_SYS_CLOCK_EXISTS
-
 /*
- * If timer frequency is known at compile time, a simple (32-bit)
- * tick <-> ms conversion could be used for some combinations of
- * hardware timer frequency and tick rate. Otherwise precise
- * (64-bit) calculations are used.
+ * We default to using 64-bit intermediates in timescale conversions,
+ * but if the HW timer cycles/sec, ticks/sec and ms/sec are all known
+ * to be nicely related, then we can cheat with 32 bits instead.
  */
 
-#if !defined(CONFIG_TIMER_READS_ITS_FREQUENCY_AT_RUNTIME)
-#if (CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC % CONFIG_SYS_CLOCK_TICKS_PER_SEC) != 0
-	#define _NEED_PRECISE_TICK_MS_CONVERSION
-#elif (MSEC_PER_SEC % CONFIG_SYS_CLOCK_TICKS_PER_SEC) != 0
-	#define _NON_OPTIMIZED_TICKS_PER_SEC
-#endif
+#ifdef CONFIG_SYS_CLOCK_EXISTS
+
+#if defined(CONFIG_TIMER_READS_ITS_FREQUENCY_AT_RUNTIME) || \
+	(MSEC_PER_SEC % CONFIG_SYS_CLOCK_TICKS_PER_SEC) || \
+	(CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC % CONFIG_SYS_CLOCK_TICKS_PER_SEC)
+#define _NEED_PRECISE_TICK_MS_CONVERSION
 #endif
 
-#if	defined(CONFIG_TIMER_READS_ITS_FREQUENCY_AT_RUNTIME) || \
-	defined(_NON_OPTIMIZED_TICKS_PER_SEC)
-	#define _NEED_PRECISE_TICK_MS_CONVERSION
-#endif
 #endif
 
 static ALWAYS_INLINE s32_t z_ms_to_ticks(s32_t ms)