--- image/decoders/nsIconDecoder.cpp
+++ image/decoders/nsIconDecoder.cpp
@@ -89,17 +89,18 @@ nsIconDecoder::ReadRowOfPixels(const cha
 {
   MOZ_ASSERT(aLength % 4 == 0, "Rows should contain a multiple of four bytes");
 
   auto result = mPipe.WritePixels<uint32_t>([&]() -> NextPixel<uint32_t> {
     if (aLength == 0) {
       return AsVariant(WriteState::NEED_MORE_DATA);  // Done with this row.
     }
 
-    uint32_t pixel = *reinterpret_cast<const uint32_t*>(aData);
+    uint32_t pixel;
+    memcpy(&pixel, aData, 4);
     aData += 4;
     aLength -= 4;
 
     return AsVariant(pixel);
   });
 
   MOZ_ASSERT(result != WriteState::FAILURE);