diff --git a/engines/default/slabs.c b/engines/default/slabs.c
index 98031281d..06448ebfd 100644
--- a/engines/default/slabs.c
+++ b/engines/default/slabs.c
@@ -748,15 +748,18 @@ static void do_smmgr_01pct_check_and_move_left(void)
             assert(smid <= sm_anchor.used_maxid);
             sm_anchor.used_01pct_clsid = smid;
         } else {
-            assert(sm_anchor.used_01pct_space == 0);
-            sm_anchor.used_01pct_clsid = sm_anchor.used_maxid;
-            sm_anchor.used_01pct_space = sm_anchor.used_slist[sm_anchor.used_maxid].space;
+            assert(sm_anchor.used_01pct_clsid > sm_anchor.used_maxid &&
+                   sm_anchor.used_01pct_space == 0);
+            /* go downward */
         }
     }
 
-    if (sm_anchor.used_01pct_space < space_standard) {
+    if (sm_anchor.used_01pct_space < space_standard ||
+        sm_anchor.used_01pct_space == 0) {
         int old_used_01pct_clsid = sm_anchor.used_01pct_clsid;
-        for (smid = old_used_01pct_clsid-1; smid >= sm_anchor.used_minid; smid--) {
+        smid = sm_anchor.used_maxid < old_used_01pct_clsid
+             ? sm_anchor.used_maxid : (old_used_01pct_clsid-1);
+        for (; smid >= sm_anchor.used_minid; smid--) {
             if (sm_anchor.used_slist[smid].space > 0) {
                 sm_anchor.used_01pct_space += sm_anchor.used_slist[smid].space;
                 if (sm_anchor.used_01pct_space >= space_standard) {
diff --git a/t/issue_ee_599.t b/t/issue_ee_599.t
new file mode 100644
index 000000000..74170d81b
--- /dev/null
+++ b/t/issue_ee_599.t
@@ -0,0 +1,81 @@
+#!/usr/bin/perl
+
+use strict;
+use Test::More tests => 27;
+use FindBin qw($Bin);
+use lib "$Bin/lib";
+use MemcachedTest;
+
+my $engine = shift;
+my $server = get_memcached($engine);
+my $sock = $server->sock;
+my $cmd;
+my $val;
+my $rst;
+my $size;
+my $stats;
+
+$size = 10;
+$cmd = "set key1 1 0 $size"; $val = "x"x$size; $rst = "STORED";
+mem_cmd_is($sock, $cmd, $val, $rst);
+
+sleep(0.01);
+$stats = mem_stats($sock, "slabs");
+is ($stats->{"SM:used_min_classid"}, 12, "$cmd confirm used_min_classid");
+is ($stats->{"SM:used_max_classid"}, 12, "$cmd confirm used_max_classid");
+is ($stats->{"SM:used_01pct_classid"}, 12, "$cmd confirm used_01pct_classid");
+is ($stats->{"SM:free_min_classid"}, 709, "$cmd confirm free_min_classid");
+is ($stats->{"SM:free_max_classid"}, -1, "$cmd confirm free_max_classid");
+is ($stats->{"SM:free_small_space"}, 0, "$cmd confirm free_small_space");
+
+$size = 3;
+$cmd = "set key2 1 0 $size"; $val = "x"x$size; $rst = "STORED";
+mem_cmd_is($sock, $cmd, $val, $rst);
+
+sleep(0.01);
+$stats = mem_stats($sock, "slabs");
+is ($stats->{"SM:used_min_classid"}, 11, "$cmd confirm used_min_classid");
+is ($stats->{"SM:used_max_classid"}, 12, "$cmd confirm used_max_classid");
+
+$size = 20;
+$cmd = "set key3 1 0 $size"; $val = "x"x$size; $rst = "STORED";
+mem_cmd_is($sock, $cmd, $val, $rst);
+
+sleep(0.01);
+$stats = mem_stats($sock, "slabs");
+is ($stats->{"SM:used_min_classid"}, 11, "$cmd confirm used_min_classid");
+is ($stats->{"SM:used_max_classid"}, 13, "$cmd confirm used_max_classid");
+
+$size = 3;
+$cmd = "set key4 1 0 $size"; $val = "x"x$size; $rst = "STORED";
+mem_cmd_is($sock, $cmd, $val, $rst);
+
+
+# make free space
+$cmd = "delete key1"; $rst = "DELETED";
+mem_cmd_is($sock, $cmd, "", $rst);
+
+sleep(0.01);
+$stats = mem_stats($sock, "slabs");
+is ($stats->{"SM:used_min_classid"}, 11, "$cmd confirm used_min_classid");
+is ($stats->{"SM:used_max_classid"}, 13, "$cmd confirm used_max_classid");
+is ($stats->{"SM:used_01pct_classid"}, 13, "$cmd confirm used_01pct_classid");
+is ($stats->{"SM:free_min_classid"}, 12, "$cmd confirm free_min_classid");
+is ($stats->{"SM:free_max_classid"}, 12, "$cmd confirm free_max_classid");
+
+$cmd = "delete key3"; $rst = "DELETED";
+mem_cmd_is($sock, $cmd, "", $rst);
+
+sleep(0.01);
+$stats = mem_stats($sock, "slabs");
+is ($stats->{"SM:used_min_classid"}, 11, "$cmd confirm used_min_classid");
+is ($stats->{"SM:used_max_classid"}, 11, "$cmd confirm used_max_classid");
+is ($stats->{"SM:used_01pct_classid"}, 11, "$cmd confirm used_01pct_classid");
+is ($stats->{"SM:free_min_classid"}, 12, "$cmd confirm free_min_classid");
+is ($stats->{"SM:free_max_classid"}, 13, "$cmd confirm free_max_classid");
+# Previously, there was a phenomenon in
+# which free_small_space was calculated to be larger than 0
+is ($stats->{"SM:free_small_space"}, 0, "$cmd confirm free_small_space");
+
+# after test
+release_memcached($engine, $server);
diff --git a/t/tlist/engine_default_b.txt b/t/tlist/engine_default_b.txt
index f5dba4733..eb0322b51 100644
--- a/t/tlist/engine_default_b.txt
+++ b/t/tlist/engine_default_b.txt
@@ -70,6 +70,7 @@
 ./t/issue_68.t
 ./t/issue_70.t
 ./t/issue_arcus_151.t
+./t/issue_ee_599.t
 ./t/item_size_max.t
 ./t/line-lengths.t
 ./t/longkey.t
diff --git a/t/tlist/engine_default_s.txt b/t/tlist/engine_default_s.txt
index 8f15c1f18..82af99655 100644
--- a/t/tlist/engine_default_s.txt
+++ b/t/tlist/engine_default_s.txt
@@ -66,6 +66,7 @@
 ./t/issue_68.t
 ./t/issue_70.t
 ./t/issue_arcus_151.t
+./t/issue_ee_599.t
 ./t/item_size_max.t
 ./t/line-lengths.t
 ./t/longkey.t