diff --git a/gfx/angle/src/libGLESv2/VertexDataManager.cpp b/gfx/angle/src/libGLESv2/VertexDataManager.cpp
--- a/gfx/angle/src/libGLESv2/VertexDataManager.cpp
+++ b/gfx/angle/src/libGLESv2/VertexDataManager.cpp
@@ -714,17 +714,17 @@ void StaticVertexBuffer::reserveRequired
     {
         // Already allocated
     }
     else UNREACHABLE();   // Static vertex buffers can't be resized
 
     mRequiredSpace = 0;
 }
 
-UINT StaticVertexBuffer::lookupAttribute(const VertexAttribute &attribute)
+std::size_t StaticVertexBuffer::lookupAttribute(const VertexAttribute &attribute)
 {
     for (unsigned int element = 0; element < mCache.size(); element++)
     {
         if (mCache[element].type == attribute.mType &&  mCache[element].size == attribute.mSize && mCache[element].normalized == attribute.mNormalized)
         {
             if (mCache[element].attributeOffset == attribute.mOffset % attribute.stride())
             {
                 return mCache[element].streamOffset;
diff --git a/gfx/angle/src/libGLESv2/VertexDataManager.h b/gfx/angle/src/libGLESv2/VertexDataManager.h
--- a/gfx/angle/src/libGLESv2/VertexDataManager.h
+++ b/gfx/angle/src/libGLESv2/VertexDataManager.h
@@ -88,17 +88,17 @@ class StaticVertexBuffer : public ArrayV
 {
   public:
     explicit StaticVertexBuffer(IDirect3DDevice9 *device);
     ~StaticVertexBuffer();
 
     void *map(const VertexAttribute &attribute, std::size_t requiredSpace, std::size_t *streamOffset);
     void reserveRequiredSpace();
 
-    UINT lookupAttribute(const VertexAttribute &attribute);   // Returns the offset into the vertex buffer, or -1 if not found
+    std::size_t lookupAttribute(const VertexAttribute &attribute);   // Returns the offset into the vertex buffer, or -1 if not found
 
   private:
     struct VertexElement
     {
         GLenum type;
         GLint size;
         bool normalized;
         int attributeOffset;