diff --git a/Kernel/API/POSIX/unistd.h b/Kernel/API/POSIX/unistd.h
index 1058ea75ef..30bbb6ffc9 100644
--- a/Kernel/API/POSIX/unistd.h
+++ b/Kernel/API/POSIX/unistd.h
@@ -39,6 +39,7 @@ enum {
     _SC_GETPW_R_SIZE_MAX,
     _SC_CLK_TCK,
     _SC_SYMLOOP_MAX,
+    _SC_MAPPED_FILES,
 };
 
 #define _SC_MONOTONIC_CLOCK _SC_MONOTONIC_CLOCK
@@ -51,6 +52,7 @@ enum {
 #define _SC_GETPW_R_SIZE_MAX _SC_GETPW_R_SIZE_MAX
 #define _SC_CLK_TCK _SC_CLK_TCK
 #define _SC_SYMLOOP_MAX _SC_SYMLOOP_MAX
+#define _SC_MAPPED_FILES _SC_MAPPED_FILES
 
 #ifdef __cplusplus
 }