STM8S TIM4 vs TIM2

Hello, I'm curious why TIM2 is correctly repeating in my code, whereas TIM4 with equivalent settings is not.

In this code, the TIM2 indicator (fired by the TIM2 interrupt) is blinking twice a second (clock set to LSI, meaning 128kHz). I would expect the TIM4 indicator (fired by the TIM4 interrupt) to do the same; but it is being triggered immediately and much faster: so fast that to the eye it appears as a constant on.

The reference manual RM0016 and datasheet DS7147 indicate that, given similar settings, both timers should be exhibiting similar behavior. What am I missing?

Here's the code:

; some typical setup hidden before this point
 ; PD3 is on, indicating LSI is clock source
 ld a, CLK_SWR
 cp a, #0xd2
 jrne 1$
 bset PD_ODR, #3

 ; timer setup
 sim
 ; F_Master Prescalar tim clk
 ; 128_000 Hz / 1024 = 125
 mov TIM2_PSCR, #0b1010 ; 2 ** 0b1010 = 1024 prescaler
 mov TIM2_ARRH, #0d0
 mov TIM2_ARRL, #0d125
 bset TIM2_IER, #0 ; UIE: Update interrupt enable
 bset TIM2_CR1, #0 ; CEN: Counter enable

 ; same as TIM2
 mov TIM4_PSCR, #0b1010
 mov TIM4_ARR, #0d125
 bset TIM4_IER, #0 ; UIE: Update interrupt enable
 bset TIM4_CR1, #0 ; CEN: Counter enable
 rim

 ; loop
 1$:
 wfi
 jp 1$

tim2_up_isr:
 bres TIM2_SR1, #0 ; UIF: Update interrupt flag
 ; blinks twice per second
 bcpl PC_ODR, #6
 iret

tim4_up_isr:
 bres TIM4_SR, #0 ; UIF: Update interrupt flag
 ; blinks continuously
 bcpl PC_ODR, #7
 iret