diff --git a/src/gif.imageio/gif.h b/src/gif.imageio/gif.h
index afbe3d8050..624f05f8cf 100644
--- a/src/gif.imageio/gif.h
+++ b/src/gif.imageio/gif.h
@@ -340,7 +340,8 @@ void GifSplitPalette(uint8_t* image, int numPixels, int firstElt, int lastElt, i
     if(bRange > gRange) splitCom = 2;
     if(rRange > bRange && rRange > gRange) splitCom = 0;
 
-    int subPixelsA = numPixels * (splitElt - firstElt) / (lastElt - firstElt);
+    int subPixelsA = (int)(int64_t(numPixels) * (splitElt - firstElt)
+                           / (lastElt - firstElt));
     int subPixelsB = numPixels-subPixelsA;
 
     GifPartitionByMedian(image, 0, numPixels, splitCom, subPixelsA);
@@ -388,7 +389,7 @@ void GifMakePalette( const uint8_t* lastFrame, const uint8_t* nextFrame, uint32_
 
     // SplitPalette is destructive (it sorts the pixels by color) so
     // we must create a copy of the image for it to destroy
-    size_t imageSize = (size_t)(width * height * 4 * sizeof(uint8_t));
+    size_t imageSize = size_t(width) * size_t(height) * 4 * sizeof(uint8_t);
     uint8_t* destroyableImage = (uint8_t*)GIF_TEMP_MALLOC(imageSize);
     memcpy(destroyableImage, nextFrame, imageSize);
 
@@ -789,7 +790,7 @@ bool GifBegin( GifWriter<FILE>* writer, const char* filename, uint32_t width, ui
     writer->firstFrame = true;
 
     // allocate
-    writer->oldImage = (uint8_t*)GIF_MALLOC(width*height*4);
+    writer->oldImage = (uint8_t*)GIF_MALLOC(uint64_t(width)*uint64_t(height)*4);
 
     fputs("GIF89a", writer->f);
 
diff --git a/src/gif.imageio/gifinput.cpp b/src/gif.imageio/gifinput.cpp
index c48a82cbaa..8ea1aaf70a 100644
--- a/src/gif.imageio/gifinput.cpp
+++ b/src/gif.imageio/gifinput.cpp
@@ -206,7 +206,8 @@ GIFInput::read_native_scanline(int subimage, int miplevel, int y, int /*z*/,
     if (y < 0 || y > m_spec.height || !m_canvas.size())
         return false;
 
-    memcpy(data, &m_canvas[y * m_spec.width * m_spec.nchannels],
+    memcpy(data,
+           &m_canvas[int64_t(y) * int64_t(m_spec.width) * m_spec.nchannels],
            m_spec.width * m_spec.nchannels);
 
     return true;
@@ -365,8 +366,9 @@ GIFInput::read_subimage_data()
                         fscanline[wx], wx, y, colormap_count);
                     return false;
                 }
-                int x   = window_left + wx;
-                int idx = m_spec.nchannels * (y * m_spec.width + x);
+                int x       = window_left + wx;
+                int64_t idx = m_spec.nchannels
+                              * (int64_t(y) * m_spec.width + x);
                 if (0 <= x && x < m_spec.width) {
                     m_canvas[idx]     = colormap[fscanline[wx]].Red;
                     m_canvas[idx + 1] = colormap[fscanline[wx]].Green;