diff --git a/src/amiga.c b/src/amiga.c
index bfbae43..17b4ce1 100644
--- a/src/amiga.c
+++ b/src/amiga.c
@@ -155,7 +155,7 @@ void amiga_init(void)
 
     /* We map PB4 (KBCLK) to TIM3,CH1 and use its input filter and edge 
      * detector to generate interrupts on clock transitions. */
-    afio->mapr |= AFIO_MAPR_TIM3_REMAP_PARTIAL;
+
     /* f_sampling = 72MHz/8 = 9MHz, N=8 -> must be stable for 889us. */
     tim3->ccmr1 = TIM_CCMR1_CC1S(TIM_CCS_INPUT_TI1) | TIM_CCMR1_IC1F(9);
     tim3->ccer = TIM_CCER_CC1E | TIM_CCER_CC1P; /* Falling edge */
diff --git a/src/stm32f10x.c b/src/stm32f10x.c
index 5159ca3..47c5a5d 100644
--- a/src/stm32f10x.c
+++ b/src/stm32f10x.c
@@ -135,8 +135,11 @@ static void peripheral_init(void)
 
     rcc->ahbenr = RCC_AHBENR_DMA1EN;
 
-    /* Turn off serial-wire JTAG and reclaim the GPIOs. */
-    afio->mapr = AFIO_MAPR_SWJ_CFG_JTAGDISABLE;
+    /* Turn off serial-wire JTAG and reclaim the GPIOs.
+     * Amiga keyboard map PB4 (KBCLK) to TIM3,CH1 and use its input filter
+     * and edge detector to generate interrupts on clock transitions. */
+    afio->mapr = (AFIO_MAPR_SWJ_CFG_JTAGDISABLE
+                 | AFIO_MAPR_TIM3_REMAP_PARTIAL);
 
     /* All pins in a stable state. */
     gpio_init(gpioa);