diff --git a/libmicrokit/include/microkit.h b/libmicrokit/include/microkit.h
index 4c664f40a..076717909 100644
--- a/libmicrokit/include/microkit.h
+++ b/libmicrokit/include/microkit.h
@@ -8,9 +8,6 @@
 
 #pragma once
 
-#include <stdint.h>
-#include <stdbool.h>
-
 #define __thread
 #include <sel4/sel4.h>
 
@@ -31,7 +28,7 @@ microkit_msginfo protected(microkit_channel ch, microkit_msginfo msginfo);
 
 extern char microkit_name[16];
 /* These next three variables are so our PDs can combine a signal with the next Recv syscall */
-extern bool have_signal;
+extern seL4_Bool have_signal;
 extern seL4_CPtr signal;
 extern seL4_MessageInfo_t signal_msg;
 
@@ -60,27 +57,27 @@ static inline microkit_msginfo microkit_ppcall(microkit_channel ch, microkit_msg
     return seL4_Call(BASE_ENDPOINT_CAP + ch, msginfo);
 }
 
-static inline microkit_msginfo microkit_msginfo_new(uint64_t label, uint16_t count)
+static inline microkit_msginfo microkit_msginfo_new(seL4_Word label, seL4_Uint16 count)
 {
     return seL4_MessageInfo_new(label, 0, 0, count);
 }
 
-static inline uint64_t microkit_msginfo_get_label(microkit_msginfo msginfo)
+static inline seL4_Word microkit_msginfo_get_label(microkit_msginfo msginfo)
 {
     return seL4_MessageInfo_get_label(msginfo);
 }
 
-static inline uint64_t microkit_msginfo_get_count(microkit_msginfo msginfo)
+static inline seL4_Word microkit_msginfo_get_count(microkit_msginfo msginfo)
 {
     return seL4_MessageInfo_get_length(msginfo);
 }
 
-static void microkit_mr_set(uint8_t mr, uint64_t value)
+static void microkit_mr_set(seL4_Uint8 mr, seL4_Word value)
 {
     seL4_SetMR(mr, value);
 }
 
-static uint64_t microkit_mr_get(uint8_t mr)
+static seL4_Word microkit_mr_get(seL4_Uint8 mr)
 {
     return seL4_GetMR(mr);
 }
diff --git a/libmicrokit/src/main.c b/libmicrokit/src/main.c
index 3ba35a352..53ed337e7 100644
--- a/libmicrokit/src/main.c
+++ b/libmicrokit/src/main.c
@@ -21,7 +21,9 @@ char _stack[4096]  __attribute__((__aligned__(16)));
 
 bool passive;
 char microkit_name[16];
-bool have_signal = false;
+/* We use seL4 typedefs as this variable is exposed to the libmicrokit header
+ * and we do not want to rely on compiler built-in defines. */
+seL4_Bool have_signal = seL4_False;
 seL4_CPtr signal;
 seL4_MessageInfo_t signal_msg;
 
@@ -58,7 +60,7 @@ static void handler_loop(void)
             tag = seL4_ReplyRecv(INPUT_CAP, reply_tag, &badge, REPLY_CAP);
         } else if (have_signal) {
             tag = seL4_NBSendRecv(signal, signal_msg, INPUT_CAP, &badge, REPLY_CAP);
-            have_signal = false;
+            have_signal = seL4_False;
         } else {
             tag = seL4_Recv(INPUT_CAP, &badge, REPLY_CAP);
         }
@@ -94,7 +96,7 @@ void main(void)
      * We delay this signal so we are ready waiting on a recv() syscall
      */
     if (passive) {
-        have_signal = true;
+        have_signal = seL4_True;
         signal_msg = seL4_MessageInfo_new(0, 0, 0, 1);
         seL4_SetMR(0, 0);
         signal = (MONITOR_EP);