diff --git a/lib/mayaHydra/hydraExtensions/adapters/materialAdapter.cpp b/lib/mayaHydra/hydraExtensions/adapters/materialAdapter.cpp
index b69c5b829..e807ab2b5 100644
--- a/lib/mayaHydra/hydraExtensions/adapters/materialAdapter.cpp
+++ b/lib/mayaHydra/hydraExtensions/adapters/materialAdapter.cpp
@@ -263,7 +263,10 @@ class MayaHydraShadingEngineAdapter : public MayaHydraMaterialAdapter
         }
 
         // Construct a MaterialX document
-        auto mtlxDocStr = mtlxDocPlug.asString();
+        const MString mtlxDocStr = mtlxDocPlug.asString();
+        if (0 == mtlxDocStr.length()) {
+            return false;
+        }
         auto mtlxDoc = MaterialX::createDocument();
         MaterialX::readFromXmlString(mtlxDoc, mtlxDocStr.asChar());