diff --git a/simgear/scene/material/Effect.hxx b/simgear/scene/material/Effect.hxx
index cb4341bb..0966dc1a 100644
--- a/simgear/scene/material/Effect.hxx
+++ b/simgear/scene/material/Effect.hxx
@@ -176,6 +176,8 @@ Effect* makeEffect(SGPropertyNode* prop,
 bool makeParametersFromStateSet(SGPropertyNode* paramRoot,
                                 const osg::StateSet* ss);
 
+void clearEffectCache();
+
 namespace effect
 {
 /**
diff --git a/simgear/scene/material/makeEffect.cxx b/simgear/scene/material/makeEffect.cxx
index 06bf47b2..4abdd4a2 100644
--- a/simgear/scene/material/makeEffect.cxx
+++ b/simgear/scene/material/makeEffect.cxx
@@ -270,4 +270,10 @@ Effect* makeEffect(SGPropertyNode* prop,
     return effect.release();
 }
 
+void clearEffectCache()
+{
+    OpenThreads::ScopedLock<OpenThreads::ReentrantMutex> lock(effectMutex);
+    effectMap.clear();
+}
+
 }