diff --git a/dom/canvas/WebGLBuffer.cpp b/dom/canvas/WebGLBuffer.cpp
index 4ac02bd414d..357b9873269 100644
--- a/dom/canvas/WebGLBuffer.cpp
+++ b/dom/canvas/WebGLBuffer.cpp
@@ -264,7 +264,7 @@ void WebGLBuffer::InvalidateCacheRange(uint64_t byteOffset,
   for (const auto& cur : mIndexRanges) {
     const auto& range = cur.first;
     const auto& indexByteSize = IndexByteSizeByType(range.type);
-    const auto rangeBegin = range.byteOffset * indexByteSize;
+    const auto rangeBegin = range.byteOffset;
     const auto rangeEnd =
         rangeBegin + uint64_t(range.indexCount) * indexByteSize;
     if (rangeBegin >= updateEnd || rangeEnd <= updateBegin) continue;