diff --git a/src/webp.imageio/webpinput.cpp b/src/webp.imageio/webpinput.cpp
index 09cc08c4cd..bbe35d9822 100644
--- a/src/webp.imageio/webpinput.cpp
+++ b/src/webp.imageio/webpinput.cpp
@@ -214,8 +214,11 @@ WebpInput::open(const std::string& name, ImageSpec& spec,
     // Make space for the decoded image
     m_decoded_image.reset(new uint8_t[m_spec.image_bytes()]);
 
-    if (config.get_int_attribute("oiio:UnassociatedAlpha", 0) == 1)
+    if (config.get_int_attribute("oiio:UnassociatedAlpha", 0) == 1) {
         m_keep_unassociated_alpha = true;
+        if (m_spec.alpha_channel != -1)
+            m_spec.attribute("oiio:UnassociatedAlpha", 1);
+    }
 
     seek_subimage(0, 0);
     spec = m_spec;
diff --git a/testsuite/webp/ref/out-webp1.1.txt b/testsuite/webp/ref/out-webp1.1.txt
index f7e0d095de..92ec6d9f0f 100644
--- a/testsuite/webp/ref/out-webp1.1.txt
+++ b/testsuite/webp/ref/out-webp1.1.txt
@@ -18,3 +18,9 @@ Reading ../oiio-images/webp/4.webp
     SHA-1: 8F42E3DCCE6FE15146BA06C440C15B7831F60572
     channel list: R, G, B
     oiio:ColorSpace: "srgb_rec709_scene"
+Reading rgba.webp
+rgba.webp            :   64 x   64, 4 channel, uint8 webp
+    SHA-1: 897256B6709E1A4DA9DABA92B6BDE39CCFCCD8C1
+    channel list: R, G, B, A
+    oiio:ColorSpace: "srgb_rec709_scene"
+    oiio:UnassociatedAlpha: 1
diff --git a/testsuite/webp/run.py b/testsuite/webp/run.py
index a0a5c53510..3e61dd5d81 100755
--- a/testsuite/webp/run.py
+++ b/testsuite/webp/run.py
@@ -11,3 +11,6 @@
     # a lossy format and is not stable under the round trip
     # command += rw_command (OIIO_TESTSUITE_IMAGEDIR, f,
     #                        extraargs='-attrib compression lossless')
+
+command += oiiotool ("--create 64x64 4 -o rgba.webp")
+command += info_command ("rgba.webp", "--iconfig oiio:UnassociatedAlpha 1", safematch=True)