diff --git a/dlls/ntdll/thread.c b/dlls/ntdll/thread.c
index b1006080dd0..eaea02c4f94 100644
--- a/dlls/ntdll/thread.c
+++ b/dlls/ntdll/thread.c
@@ -131,7 +131,7 @@ static inline NTSTATUS init_teb( TEB *teb )
  *
  * Make sure the unicode string doesn't point beyond the end pointer
  */
-static inline void fix_unicode_string( UNICODE_STRING *str, char *end_ptr )
+static inline void fix_unicode_string( UNICODE_STRING *str, const char *end_ptr )
 {
     if ((char *)str->Buffer >= end_ptr)
     {
diff --git a/dlls/ntdll/virtual.c b/dlls/ntdll/virtual.c
index 5964258c2df..7f42f59b8ba 100644
--- a/dlls/ntdll/virtual.c
+++ b/dlls/ntdll/virtual.c
@@ -366,9 +366,9 @@ static void add_reserved_area( void *addr, size_t size )
  *
  * Check if an address range goes beyond a given limit.
  */
-static inline int is_beyond_limit( void *addr, size_t size, void *limit )
+static inline int is_beyond_limit( const void *addr, size_t size, const void *limit )
 {
-    return (limit && (addr >= limit || (char *)addr + size > (char *)limit));
+    return (limit && (addr >= limit || (const char *)addr + size > (const char *)limit));
 }