diff --git a/include/libopencm3/stm32/f1/gpio.h b/include/libopencm3/stm32/f1/gpio.h
index 580c501c..1e97b734 100644
--- a/include/libopencm3/stm32/f1/gpio.h
+++ b/include/libopencm3/stm32/f1/gpio.h
@@ -929,7 +929,7 @@ BEGIN_DECLS
 
 void gpio_set_mode(u32 gpioport, u8 mode, u8 cnf, u16 gpios);
 void gpio_set_eventout(u8 evoutport, u8 evoutpin);
-void gpio_primary_remap(u8 swjenable, u32 maps);
+void gpio_primary_remap(u32 swjenable, u32 maps);
 void gpio_secondary_remap(u32 maps);
 
 END_DECLS
diff --git a/lib/stm32/f1/gpio.c b/lib/stm32/f1/gpio.c
index 2b33cad9..cbb6b9d3 100644
--- a/lib/stm32/f1/gpio.c
+++ b/lib/stm32/f1/gpio.c
@@ -162,9 +162,9 @@ value cannot be ascertained from the hardware.
 		@ref afio_remap_usart3. For connectivity line devices only @ref afio_remap_cld are
         also available.
 */
-void gpio_primary_remap(u8 swjdisable, u32 maps)
+void gpio_primary_remap(u32 swjdisable, u32 maps)
 {
-	AFIO_MAPR |= swjdisable | (maps & 0x1FFFFF);
+	AFIO_MAPR |= (swjdisable & AFIO_MAPR_SWJ_MASK) | (maps & 0x1FFFFF);
 }
 
 /*-----------------------------------------------------------------------------*/