diff --git a/src/dec/buffer.c b/src/dec/buffer.c
index 42feac74..6272424f 100644
--- a/src/dec/buffer.c
+++ b/src/dec/buffer.c
@@ -67,7 +67,9 @@ static VP8StatusCode CheckDecBuffer(const WebPDecBuffer* const buffer) {
   } else {    // RGB checks
     const WebPRGBABuffer* const buf = &buffer->u.RGBA;
     const int stride = abs(buf->stride);
-    const uint64_t size = (uint64_t)stride * height;
+    // strictly speaking, the very last (or first, if flipped) row
+    // doesn't require padding.
+    const uint64_t size = (uint64_t)stride * (height - 1) + width;
     ok &= (size <= buf->size);
     ok &= (stride >= width * kModeBpp[mode]);
     ok &= (buf->rgba != NULL);