diff --git a/modules/plugin/base/src/ns4xPlugin.cpp b/modules/plugin/base/src/ns4xPlugin.cpp
index 978854f5fcd2..d4d0743bb1cd 100644
--- a/modules/plugin/base/src/ns4xPlugin.cpp
+++ b/modules/plugin/base/src/ns4xPlugin.cpp
@@ -861,7 +861,10 @@ ns4xPlugin::_setvalue(NPP npp, NPPVariable variable, void *result)
     switch (variable)
     {
       case NPPVpluginWindowBool:
-        return inst->SetWindowless(*((NPBool *)result));
+      {
+        NPBool bWindowless = !(*((NPBool *)result));
+        return inst->SetWindowless(bWindowless);
+      }
 
       case NPPVpluginTransparentBool:
         return inst->SetTransparent(*((NPBool *)result));
diff --git a/modules/plugin/nglsrc/ns4xPlugin.cpp b/modules/plugin/nglsrc/ns4xPlugin.cpp
index 978854f5fcd2..d4d0743bb1cd 100644
--- a/modules/plugin/nglsrc/ns4xPlugin.cpp
+++ b/modules/plugin/nglsrc/ns4xPlugin.cpp
@@ -861,7 +861,10 @@ ns4xPlugin::_setvalue(NPP npp, NPPVariable variable, void *result)
     switch (variable)
     {
       case NPPVpluginWindowBool:
-        return inst->SetWindowless(*((NPBool *)result));
+      {
+        NPBool bWindowless = !(*((NPBool *)result));
+        return inst->SetWindowless(bWindowless);
+      }
 
       case NPPVpluginTransparentBool:
         return inst->SetTransparent(*((NPBool *)result));