diff --git a/src/osg/Uniform.cpp b/src/osg/Uniform.cpp
index 71ebc1d6a..a2452118c 100644
--- a/src/osg/Uniform.cpp
+++ b/src/osg/Uniform.cpp
@@ -59,11 +59,15 @@ void Uniform::addParent(osg::StateSet* object)
 {
     OSG_DEBUG_FP<<"Uniform Adding parent"<<std::endl;
 
+    OpenThreads::ScopedPointerLock<OpenThreads::Mutex> lock(getRefMutex());
+
     _parents.push_back(object);
 }
 
 void Uniform::removeParent(osg::StateSet* object)
 {
+    OpenThreads::ScopedPointerLock<OpenThreads::Mutex> lock(getRefMutex());
+
     ParentList::iterator pitr = std::find(_parents.begin(),_parents.end(),object);
     if (pitr!=_parents.end()) _parents.erase(pitr);
 }