diff --git a/include/stdlib.h b/include/stdlib.h
index a76f8edb9a78..086cdddc0f10 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -124,7 +124,7 @@ int	 mbtowc(wchar_t *, const char *, size_t);
 size_t	 wcstombs(char *, const wchar_t *, size_t);
 
 #if !defined(_ANSI_SOURCE) && !defined(_POSIX_SOURCE)
-extern char *_malloc_options;
+extern const char *_malloc_options;
 extern void (*_malloc_message)(char *p1, char *p2, char *p3, char *p4);
 
 int	 putenv(const char *);
diff --git a/lib/libc/stdlib/malloc.3 b/lib/libc/stdlib/malloc.3
index 4271ff80c576..a78d83016394 100644
--- a/lib/libc/stdlib/malloc.3
+++ b/lib/libc/stdlib/malloc.3
@@ -56,8 +56,8 @@
 .Fn reallocf "void *ptr" "size_t size"
 .Ft void
 .Fn free "void *ptr"
-.Ft char *
-.Va _malloc_options
+.Ft const char *
+.Va _malloc_options;
 .Ft void
 .Fn \*(lp*_malloc_message\*(rp "char *p1" "char *p2" "char *p3" "char *p4"
 .Sh DESCRIPTION
diff --git a/lib/libc/stdlib/malloc.c b/lib/libc/stdlib/malloc.c
index 43aad2d79211..d2371bdd69a2 100644
--- a/lib/libc/stdlib/malloc.c
+++ b/lib/libc/stdlib/malloc.c
@@ -267,7 +267,7 @@ static void *malloc_brk;
 static struct pgfree *px;
 
 /* compile-time options */
-char *_malloc_options;
+const char *_malloc_options;
 
 /* Name of the current public function */
 static char *malloc_func;