diff --git a/system/sysctl b/system/sysctl
index be379798252..ab1da5e0959 100644
--- a/system/sysctl
+++ b/system/sysctl
@@ -187,7 +187,7 @@ class SysctlModule(object):
             return ''
         elif value.lower() in BOOLEANS_TRUE:
             return '1'
-        elif not value.lower() in BOOLEANS_FALSE:
+        elif value.lower() in BOOLEANS_FALSE:
             return '0'
         else:
             return value.strip()