diff --git a/cpu/lpc2387/periph/timer.c b/cpu/lpc2387/periph/timer.c
index 515d031bed..1bedb5d9e2 100644
--- a/cpu/lpc2387/periph/timer.c
+++ b/cpu/lpc2387/periph/timer.c
@@ -73,20 +73,20 @@ static inline lpc23xx_timer_t *get_dev(tim_t tim)
     }
 }
 
-static inline void pwr_clk_and_isr(tim_t tim)
+static inline void pwr_clk_and_isr(tim_t tim, uint32_t scale)
 {
     switch (tim) {
         case 0:
             PCONP |= (1 << 1);
             PCLKSEL0 &= ~(0x03 << 2);
-            PCLKSEL0 |=  (0x01 << 2);
+            PCLKSEL0 |=  (scale << 2);
             install_irq(TIMER0_INT, &tim_isr_0, 1);
             break;
 #if TIMER_NUMOF > 1
         case 1:
             PCONP |= (1 << 2);
             PCLKSEL0 &= ~(0x03 << 4);
-            PCLKSEL0 |=  (0x01 << 4);
+            PCLKSEL0 |=  (scale << 4);
             install_irq(TIMER1_INT, &tim_isr_1, 1);
             break;
 #endif
@@ -94,7 +94,7 @@ static inline void pwr_clk_and_isr(tim_t tim)
         case 2:
             PCONP |= (1 << 22);
             PCLKSEL1 &= ~(0x03 << 12);
-            PCLKSEL1 |=  (0x01 << 12);
+            PCLKSEL1 |=  (scale << 12);
             install_irq(TIMER2_INT, &tim_isr_2, 1);
             break;
 #endif
@@ -102,7 +102,7 @@ static inline void pwr_clk_and_isr(tim_t tim)
         case 3:
             PCONP |= (1 << 23);
             PCLKSEL1 &= ~(0x03 << 14);
-            PCLKSEL1 |=  (0x01 << 14);
+            PCLKSEL1 |=  (scale << 14);
             install_irq(TIMER3_INT, &tim_isr_3, 1);
             break;
 #endif
@@ -119,16 +119,19 @@ int timer_init(tim_t tim, unsigned long freq, timer_cb_t cb, void *arg)
         return -1;
     }
 
+    uint32_t scale, prescale;
+    lpc2387_pclk_scale(CLOCK_PCLK, freq, &scale, &prescale);
+
     /* save the callback */
     isr_ctx[tim].cb = cb;
     isr_ctx[tim].arg = arg;
     /* enable power, config periph clock and install ISR vector */
-    pwr_clk_and_isr(tim);
+    pwr_clk_and_isr(tim, scale);
     /* reset timer configuration (sets the timer to timer mode) */
     dev->TCR = 0;
     dev->CTCR = 0;
     /* configure the prescaler */
-    dev->PR = (CLOCK_PCLK / freq) - 1;
+    dev->PR = prescale - 1;
     /* enable timer */
     dev->TCR = 1;
     return 0;