--- a/dom/canvas/WebGLContextBuffers.cpp
+++ b/dom/canvas/WebGLContextBuffers.cpp
@@ -318,17 +318,17 @@ WebGLContext::BufferData(GLenum target, 
         return ErrorOutOfMemory("%s: bad size", funcName);
 
     const auto& buffer = ValidateBufferSelection(funcName, target);
     if (!buffer)
         return;
 
     ////
 
-    UniquePtr<uint8_t> zeroBuffer((uint8_t*)calloc(size, 1));
+    const UniqueBuffer zeroBuffer(calloc(size, 1));
     if (!zeroBuffer)
         return ErrorOutOfMemory("%s: Failed to allocate zeros.", funcName);
 
     buffer->BufferData(target, size_t(size), zeroBuffer.get(), usage);
 }
 
 // BufferT may be one of
 // const dom::ArrayBuffer&