Index: kernel/generic/include/proc/program.h
===================================================================
--- kernel/generic/include/proc/program.h	(revision 82d515e917f3eeeff253e4aa30e493f5f632c950)
+++ kernel/generic/include/proc/program.h	(revision c81d4f18721cc59f484518c5e3819a401e3e431f)
@@ -55,10 +55,10 @@
 extern void *program_loader;
 
-extern int program_create(as_t *, uintptr_t, char *, program_t *);
-extern int program_create_from_image(void *, char *, program_t *);
-extern int program_create_loader(program_t *, char *);
+extern errno_t program_create(as_t *, uintptr_t, char *, program_t *);
+extern errno_t program_create_from_image(void *, char *, program_t *);
+extern errno_t program_create_loader(program_t *, char *);
 extern void program_ready(program_t *);
 
-extern sysarg_t sys_program_spawn_loader(char *, size_t);
+extern sys_errno_t sys_program_spawn_loader(char *, size_t);
 
 #endif
Index: kernel/generic/include/proc/task.h
===================================================================
--- kernel/generic/include/proc/task.h	(revision 82d515e917f3eeeff253e4aa30e493f5f632c950)
+++ kernel/generic/include/proc/task.h	(revision c81d4f18721cc59f484518c5e3819a401e3e431f)
@@ -156,5 +156,5 @@
 extern void task_release(task_t *);
 extern task_t *task_find_by_id(task_id_t);
-extern int task_kill(task_id_t);
+extern errno_t task_kill(task_id_t);
 extern void task_kill_self(bool) __attribute__((noreturn));
 extern void task_get_accounting(task_t *, uint64_t *, uint64_t *);
@@ -173,5 +173,5 @@
 
 #ifdef __32_BITS__
-extern sysarg_t sys_task_get_id(sysarg64_t *);
+extern sys_errno_t sys_task_get_id(sysarg64_t *);
 #endif
 
@@ -180,7 +180,7 @@
 #endif
 
-extern sysarg_t sys_task_set_name(const char *, size_t);
-extern sysarg_t sys_task_kill(task_id_t *);
-extern sysarg_t sys_task_exit(sysarg_t);
+extern sys_errno_t sys_task_set_name(const char *, size_t);
+extern sys_errno_t sys_task_kill(task_id_t *);
+extern sys_errno_t sys_task_exit(sysarg_t);
 
 #endif
Index: kernel/generic/include/proc/thread.h
===================================================================
--- kernel/generic/include/proc/thread.h	(revision 82d515e917f3eeeff253e4aa30e493f5f632c950)
+++ kernel/generic/include/proc/thread.h	(revision c81d4f18721cc59f484518c5e3819a401e3e431f)
@@ -255,5 +255,5 @@
 	thread_join_timeout((t), SYNCH_NO_TIMEOUT, SYNCH_FLAGS_NONE)
 
-extern int thread_join_timeout(thread_t *, uint32_t, unsigned int);
+extern errno_t thread_join_timeout(thread_t *, uint32_t, unsigned int);
 extern void thread_detach(thread_t *);
 
@@ -275,10 +275,10 @@
 
 /* Thread syscall prototypes. */
-extern sysarg_t sys_thread_create(uspace_arg_t *, char *, size_t,
+extern sys_errno_t sys_thread_create(uspace_arg_t *, char *, size_t,
     thread_id_t *);
-extern sysarg_t sys_thread_exit(int);
-extern sysarg_t sys_thread_get_id(thread_id_t *);
-extern sysarg_t sys_thread_usleep(uint32_t);
-extern sysarg_t sys_thread_udelay(uint32_t);
+extern sys_errno_t sys_thread_exit(int);
+extern sys_errno_t sys_thread_get_id(thread_id_t *);
+extern sys_errno_t sys_thread_usleep(uint32_t);
+extern sys_errno_t sys_thread_udelay(uint32_t);
 
 #endif