diff --git a/imageio/imageio-webp/src/main/java/com/twelvemonkeys/imageio/plugins/webp/WebPImageReader.java b/imageio/imageio-webp/src/main/java/com/twelvemonkeys/imageio/plugins/webp/WebPImageReader.java
index 5767ef8f..5570f71c 100644
--- a/imageio/imageio-webp/src/main/java/com/twelvemonkeys/imageio/plugins/webp/WebPImageReader.java
+++ b/imageio/imageio-webp/src/main/java/com/twelvemonkeys/imageio/plugins/webp/WebPImageReader.java
@@ -480,6 +480,7 @@ final class WebPImageReader extends ImageReaderBase {
 
             switch (nextChunk) {
                 case WebP.CHUNK_ALPH:
+                    seenALPH = true;
                     readAlpha(destination, param, width, height);
                     break;