diff --git a/src/read.c b/src/read.c
index 8d39b07..6289fa4 100644
--- a/src/read.c
+++ b/src/read.c
@@ -940,7 +940,7 @@ static avifResult avifDecoderItemMaxExtent(const avifDecoderItem * item, const a
                     return AVIF_RESULT_BMFF_PARSE_FAILED;
                 }
                 startOffset += remainingOffset;
-                extentSize -= remainingOffset;
+                extentSize -= (size_t)remainingOffset;
                 remainingOffset = 0;
             }
         }
@@ -3085,7 +3085,7 @@ static avifResult avifDecoderPrepareSample(avifDecoder * decoder, avifDecodeSamp
 
             avifDecoderItem * item = avifMetaFindItem(decoder->data->meta, sample->itemID);
             avifROData itemContents;
-            avifResult readResult = avifDecoderItemRead(item, decoder->io, &itemContents, sample->offset, bytesToRead, &decoder->diag);
+            avifResult readResult = avifDecoderItemRead(item, decoder->io, &itemContents, (size_t)sample->offset, bytesToRead, &decoder->diag);
             if (readResult != AVIF_RESULT_OK) {
                 return readResult;
             }