diff --git a/include/exiv2/webpimage.hpp b/include/exiv2/webpimage.hpp
index 456b2122..bd8be56c 100644
--- a/include/exiv2/webpimage.hpp
+++ b/include/exiv2/webpimage.hpp
@@ -93,7 +93,7 @@ namespace Exiv2 {
                              byte *header, long header_size);
         bool equalsWebPTag(Exiv2::DataBuf& buf ,const char* str);
         void debugPrintHex(byte *data, long size);
-        void decodeChunks(uint32_t filesize);
+        void decodeChunks(long filesize);
         void inject_VP8X(BasicIo& iIo, bool has_xmp, bool has_exif,
                          bool has_alpha, bool has_icc, int width,
                          int height);
diff --git a/src/webpimage.cpp b/src/webpimage.cpp
index e66d577c..15069cb7 100644
--- a/src/webpimage.cpp
+++ b/src/webpimage.cpp
@@ -500,13 +500,14 @@ namespace Exiv2 {
 
         readOrThrow(*io_, data, WEBP_TAG_SIZE * 3, Exiv2::kerCorruptedMetadata);
 
-        const uint32_t filesize = Exiv2::getULong(data + WEBP_TAG_SIZE, littleEndian) + 8;
-        enforce(filesize <= io_->size(), Exiv2::kerCorruptedMetadata);
+        const long filesize = Exiv2::getULong(data + WEBP_TAG_SIZE, littleEndian) + 8;
+        enforce(0 <= filesize, Exiv2::kerCorruptedMetadata);
+        enforce((size_t)filesize <= io_->size(), Exiv2::kerCorruptedMetadata);
         WebPImage::decodeChunks(filesize);
 
     } // WebPImage::readMetadata
 
-    void WebPImage::decodeChunks(uint32_t filesize)
+    void WebPImage::decodeChunks(long filesize)
     {
         DataBuf   chunkId(5);
         byte      size_buff[WEBP_TAG_SIZE];
@@ -517,10 +518,11 @@ namespace Exiv2 {
 #endif
 
         chunkId.pData_[4] = '\0' ;
-        while ( !io_->eof() && (uint64_t) io_->tell() < filesize) {
+        while (!io_->eof() && io_->tell() < filesize) {
             readOrThrow(*io_, chunkId.pData_, WEBP_TAG_SIZE, Exiv2::kerCorruptedMetadata);
             readOrThrow(*io_, size_buff, WEBP_TAG_SIZE, Exiv2::kerCorruptedMetadata);
-            const uint32_t size = Exiv2::getULong(size_buff, littleEndian);
+            const long size = Exiv2::getULong(size_buff, littleEndian);
+            enforce(0 <= size, Exiv2::kerCorruptedMetadata);
             enforce(io_->tell() <= filesize, Exiv2::kerCorruptedMetadata);
             enforce(size <= (filesize - io_->tell()), Exiv2::kerCorruptedMetadata);