diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index ce89f16404d9..8492e2b7bbb8 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1236,7 +1236,7 @@ int do_bug_frame(const struct cpu_user_regs *regs, vaddr_t pc)
 
     if ( id == BUGFRAME_run_fn )
     {
-        void (*fn)(const struct cpu_user_regs *) = (void *)regs->BUG_FN_REG;
+        bug_fn_t *fn = (void *)regs->BUG_FN_REG;
 
         fn(regs);
         return 0;
diff --git a/xen/include/xen/bug.h b/xen/include/xen/bug.h
index e8a4eea71a45..cb5138410ea7 100644
--- a/xen/include/xen/bug.h
+++ b/xen/include/xen/bug.h
@@ -99,6 +99,9 @@ struct bug_frame {
 
 #endif
 
+struct cpu_user_regs;
+typedef void bug_fn_t(const struct cpu_user_regs *regs);
+
 #ifndef run_in_exception_handler
 
 /*
@@ -132,8 +135,6 @@ struct bug_frame {
 
 #ifdef CONFIG_GENERIC_BUG_FRAME
 
-struct cpu_user_regs;
-
 /*
  * Returns a negative value in case of an error otherwise
  * BUGFRAME_{run_fn, warn, bug, assert}