diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5
index de3f35bbb..35ea9d9f6 100644
--- a/man/man5/zfs-module-parameters.5
+++ b/man/man5/zfs-module-parameters.5
@@ -301,6 +301,22 @@ rewind" (\fB-X\fR) pool import.
 Default value: 10000
 .RE
 
+.sp
+.ne 2
+.na
+\fBspa_slop_shift\fR (int)
+.ad
+.RS 12n
+Normally, we don't allow the last 3.2% (1/(2^spa_slop_shift)) of space
+in the pool to be consumed.  This ensures that we don't run the pool
+completely out of space, due to unaccounted changes (e.g. to the MOS).
+It also limits the worst-case time to allocate space.  If we have
+less than this amount of free space, most ZPL operations (e.g. write,
+create) will return ENOSPC.
+.sp
+Default value: 5
+.RE
+
 .sp
 .ne 2
 .na
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index ad9f9fe28..409dce121 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -2094,4 +2094,7 @@ MODULE_PARM_DESC(zfs_deadman_enabled, "Enable deadman timer");
 module_param(spa_asize_inflation, int, 0644);
 MODULE_PARM_DESC(spa_asize_inflation,
 	"SPA size estimate multiplication factor");
+
+module_param(spa_slop_shift, int, 0644);
+MODULE_PARM_DESC(spa_slop_shift, "Reserved free space in pool");
 #endif