diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2cfaefda5..3519407dd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ will still be backwards compatible if only `url` is specified.
 - [#178](https://github.com/influxdb/telegraf/issues/178): redis plugin, multiple server thread hang bug
 - Fix net plugin on darwin
 - [#84](https://github.com/influxdb/telegraf/issues/84): Fix docker plugin on CentOS. Thanks @neezgee!
+- [#189](https://github.com/influxdb/telegraf/pull/189): Fix mem_used_perc. Thanks @mced!
 
 ## v0.1.8 [2015-09-04]
 
diff --git a/plugins/system/ps/mem/mem_linux.go b/plugins/system/ps/mem/mem_linux.go
index 42a49a2b6..b2519ddd5 100644
--- a/plugins/system/ps/mem/mem_linux.go
+++ b/plugins/system/ps/mem/mem_linux.go
@@ -45,7 +45,7 @@ func VirtualMemory() (*VirtualMemoryStat, error) {
 	}
 	ret.Available = ret.Free + ret.Buffers + ret.Cached
 	ret.Used = ret.Total - ret.Free
-	ret.UsedPercent = float64(ret.Total-ret.Available) / float64(ret.Total) * 100.0
+	ret.UsedPercent = float64(ret.Used) / float64(ret.Total) * 100.0
 
 	return ret, nil
 }