diff --git a/include/sys/syscall.h b/include/sys/syscall.h
index 2c4b5b82f36..e6e63dee764 100644
--- a/include/sys/syscall.h
+++ b/include/sys/syscall.h
@@ -339,24 +339,30 @@
 #define SYS_fcntl                      (__SYS_filedesc + 3)
 #define SYS_lseek                      (__SYS_filedesc + 4)
 #define SYS_mmap                       (__SYS_filedesc + 5)
-#define SYS_munmap                     (__SYS_filedesc + 6)
-#define SYS_open                       (__SYS_filedesc + 7)
-#define SYS_opendir                    (__SYS_filedesc + 8)
-#define SYS_readdir                    (__SYS_filedesc + 9)
-#define SYS_rewinddir                  (__SYS_filedesc + 10)
-#define SYS_seekdir                    (__SYS_filedesc + 11)
-#define SYS_stat                       (__SYS_filedesc + 12)
-#define SYS_fstat                      (__SYS_filedesc + 13)
-#define SYS_statfs                     (__SYS_filedesc + 14)
-#define SYS_fstatfs                    (__SYS_filedesc + 15)
-#define SYS_telldir                    (__SYS_filedesc + 16)
+#define SYS_open                       (__SYS_filedesc + 6)
+#define SYS_opendir                    (__SYS_filedesc + 7)
+#define SYS_readdir                    (__SYS_filedesc + 8)
+#define SYS_rewinddir                  (__SYS_filedesc + 9)
+#define SYS_seekdir                    (__SYS_filedesc + 10)
+#define SYS_stat                       (__SYS_filedesc + 11)
+#define SYS_fstat                      (__SYS_filedesc + 12)
+#define SYS_statfs                     (__SYS_filedesc + 13)
+#define SYS_fstatfs                    (__SYS_filedesc + 14)
+#define SYS_telldir                    (__SYS_filedesc + 15)
+
+#ifdef CONFIG_FS_RAMMAP
+#  define SYS_munmap                   (__SYS_filedesc + 16)
+#  define __SYS_link                   (__SYS_filedesc + 17)
+#else
+#  define __SYS_link                   (__SYS_filedesc + 16)
+#endif
 
 #if defined(CONFIG_PSEUDOFS_SOFTLINKS)
-#  define SYS_link                     (__SYS_filedesc + 17)
-#  define SYS_readlink                 (__SYS_filedesc + 18)
-#  define __SYS_pipes                  (__SYS_filedesc + 19)
+#  define SYS_link                     (__SYS_link + 0)
+#  define SYS_readlink                 (__SYS_link + 1)
+#  define __SYS_pipes                  (__SYS_link + 2)
 #else
-#  define __SYS_pipes                  (__SYS_filedesc + 17)
+#  define __SYS_pipes                  __SYS_link
 #endif
 
 #if defined(CONFIG_PIPES) && CONFIG_DEV_PIPE_SIZE > 0
diff --git a/syscall/syscall.csv b/syscall/syscall.csv
index d4b1c3e38a6..8711a4a2477 100644
--- a/syscall/syscall.csv
+++ b/syscall/syscall.csv
@@ -48,7 +48,7 @@
 "mkdir","sys/stat.h","!defined(CONFIG_DISABLE_MOUNTPOINT)","int","FAR const char*","mode_t"
 "mkfifo2","nuttx/drivers/drivers.h","defined(CONFIG_PIPES) && CONFIG_DEV_FIFO_SIZE > 0","int","FAR const char*","mode_t","size_t"
 "mmap","sys/mman.h","","FAR void*","FAR void*","size_t","int","int","int","off_t"
-"munmap","sys/mman.h","","int","FAR void*","size_t"
+"munmap","sys/mman.h","defined(CONFIG_FS_RAMMAP)","int","FAR void *","size_t"
 "modhandle","nuttx/module.h","defined(CONFIG_MODULE)","FAR void *","FAR const char *"
 "mount","sys/mount.h","!defined(CONFIG_DISABLE_MOUNTPOINT) && defined(CONFIG_FS_READABLE)","int","const char*","const char*","const char*","unsigned long","const void*"
 "mq_close","mqueue.h","!defined(CONFIG_DISABLE_MQUEUE)","int","mqd_t"
diff --git a/syscall/syscall_lookup.h b/syscall/syscall_lookup.h
index a7e0d770ca0..24a075af111 100644
--- a/syscall/syscall_lookup.h
+++ b/syscall/syscall_lookup.h
@@ -234,7 +234,6 @@ SYSCALL_LOOKUP(up_assert,                  2, STUB_up_assert)
   SYSCALL_LOOKUP(fcntl,                    6, STUB_fcntl)
   SYSCALL_LOOKUP(lseek,                    3, STUB_lseek)
   SYSCALL_LOOKUP(mmap,                     6, STUB_mmap)
-  SYSCALL_LOOKUP(munmap,                   2, STUB_munmap)
   SYSCALL_LOOKUP(open,                     6, STUB_open)
   SYSCALL_LOOKUP(opendir,                  1, STUB_opendir)
   SYSCALL_LOOKUP(readdir,                  1, STUB_readdir)
@@ -246,6 +245,10 @@ SYSCALL_LOOKUP(up_assert,                  2, STUB_up_assert)
   SYSCALL_LOOKUP(fstatfs,                  2, STUB_fstatfs)
   SYSCALL_LOOKUP(telldir,                  1, STUB_telldir)
 
+#if defined(CONFIG_FS_RAMMAP)
+  SYSCALL_LOOKUP(munmap,                   2, STUB_munmap)
+#endif
+
 #if defined(CONFIG_PSEUDOFS_SOFTLINKS)
   SYSCALL_LOOKUP(link,                     2, STUB_link)
   SYSCALL_LOOKUP(readlink,                 3, STUB_readlink)