diff --git a/include/malloc_np.h b/include/malloc_np.h
index d3feb356b26d..24b314826cb7 100644
--- a/include/malloc_np.h
+++ b/include/malloc_np.h
@@ -33,17 +33,17 @@
 #define	_MALLOC_NP_H_
 #include <sys/cdefs.h>
 #include <sys/types.h>
+#include <stdbool.h>
 #include <strings.h>
 
 __BEGIN_DECLS
-typedef void *(chunk_alloc_t)(void *, size_t, size_t, _Bool *, _Bool *,
-    unsigned);
-typedef _Bool (chunk_dalloc_t)(void *, size_t, _Bool, unsigned);
-typedef _Bool (chunk_commit_t)(void *, size_t, size_t, size_t, unsigned);
-typedef _Bool (chunk_decommit_t)(void *, size_t, size_t, size_t, unsigned);
-typedef _Bool (chunk_purge_t)(void *, size_t, size_t, size_t, unsigned);
-typedef _Bool (chunk_split_t)(void *, size_t, size_t, size_t, _Bool, unsigned);
-typedef _Bool (chunk_merge_t)(void *, size_t, void *, size_t, _Bool, unsigned);
+typedef void *(chunk_alloc_t)(void *, size_t, size_t, bool *, bool *, unsigned);
+typedef bool (chunk_dalloc_t)(void *, size_t, bool, unsigned);
+typedef bool (chunk_commit_t)(void *, size_t, size_t, size_t, unsigned);
+typedef bool (chunk_decommit_t)(void *, size_t, size_t, size_t, unsigned);
+typedef bool (chunk_purge_t)(void *, size_t, size_t, size_t, unsigned);
+typedef bool (chunk_split_t)(void *, size_t, size_t, size_t, bool, unsigned);
+typedef bool (chunk_merge_t)(void *, size_t, void *, size_t, bool, unsigned);
 typedef struct {
 	chunk_alloc_t		*alloc;
 	chunk_dalloc_t		*dalloc;