diff --git a/indra/llrender/llvertexbuffer.cpp b/indra/llrender/llvertexbuffer.cpp
index e32589412..1b163ee4c 100644
--- a/indra/llrender/llvertexbuffer.cpp
+++ b/indra/llrender/llvertexbuffer.cpp
@@ -1850,6 +1850,7 @@ void LLVertexBuffer::unmapBuffer()
 			else
 			{
 				stop_glerror();
+				glBufferDataARB(GL_ARRAY_BUFFER_ARB, getSize(), NULL, mUsage);
 				glBufferSubDataARB(GL_ARRAY_BUFFER_ARB, 0, getSize(), (U8*) mMappedData);
 				stop_glerror();
 			}
@@ -1916,6 +1917,7 @@ void LLVertexBuffer::unmapBuffer()
 			else
 			{
 				stop_glerror();
+				glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB, getIndicesSize(), NULL, mUsage);
 				glBufferSubDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0, getIndicesSize(), (U8*) mMappedIndexData);
 				stop_glerror();
 			}