Using one timer as prescaler for another timer STM32F103RB

Hello,
STM32F103RB microcontroller.
I want to use Using one timer as prescaler for another timer mode (see figures below).

I want the slave timer to increment its counter every time the master timer generates update events. But the slave timer does this regardless of the update event (incrementing occurs constantly). I can't understand why. Tell me what I did wrong? I'm attaching the code.

#include "stm32f1xx.h"

static void init_tim3(void);
static void init_tim4(void);

static void init_tim3(void)
{
	TIM3->CR1 &= ~0x00000001;
	TIM3->CR2 |= 0x0020;
	TIM3->PSC = 0x00000000;
	TIM3->ARR = 0xFFFF;
	TIM3->CNT = 0x0000;
	TIM3->SR &= ~0x0001;
	TIM3->DIER |= 0x0001;
	//TIM3->CR1 |= 0x00000001;
}

static void init_tim4(void)
{
	TIM4->CR1 &= ~0x00000001;
	TIM4->SMCR |= 0x0020;
	TIM4->SMCR |= 0x0007;
	TIM4->PSC = 0x00000000;
	TIM4->ARR = 0x007A;
	TIM4->CNT = 0x0000;
	//TIM4->CR1 |= 0x00000001;
}

void init_tim3_tim4(void)
{
	init_tim3();
	init_tim4();
	TIM3->CR1 |= 0x00000001;
	TIM4->CR1 |= 0x00000001;
}