diff --git a/dom/canvas/WebGLTexture.h b/dom/canvas/WebGLTexture.h
index da3056e73544..89d278d352ae 100644
--- a/dom/canvas/WebGLTexture.h
+++ b/dom/canvas/WebGLTexture.h
@@ -249,7 +249,7 @@ protected:
                                    GLint zOffset, uint32_t width, uint32_t height,
                                    uint32_t depth,
                                    WebGLTexture::ImageInfo** const out_imageInfo);
-    bool ValidateCopyTexImageForFeedback(const char* funcName, uint32_t level) const;
+    bool ValidateCopyTexImageForFeedback(const char* funcName, uint32_t level, GLint layer = 0) const;
 
     bool ValidateUnpack(const char* funcName, const webgl::TexUnpackBlob* blob,
                         bool isFunc3D, const webgl::PackingInfo& srcPI) const;
diff --git a/dom/canvas/WebGLTextureUpload.cpp b/dom/canvas/WebGLTextureUpload.cpp
index f333c802b10a..0f76a9c6114b 100644
--- a/dom/canvas/WebGLTextureUpload.cpp
+++ b/dom/canvas/WebGLTextureUpload.cpp
@@ -1918,7 +1918,7 @@ ValidateCopyDestUsage(const char* funcName, WebGLContext* webgl,
 }
 
 bool
-WebGLTexture::ValidateCopyTexImageForFeedback(const char* funcName, uint32_t level) const
+WebGLTexture::ValidateCopyTexImageForFeedback(const char* funcName, uint32_t level, GLint layer) const
 {
     const auto& fb = mContext->mBoundReadFramebuffer;
     if (fb) {
@@ -1926,6 +1926,7 @@ WebGLTexture::ValidateCopyTexImageForFeedback(const char* funcName, uint32_t lev
         MOZ_ASSERT(attach);
 
         if (attach->Texture() == this &&
+            attach->Layer() == layer &&
             uint32_t(attach->MipLevel()) == level)
         {
             // Note that the TexImageTargets *don't* have to match for this to be
@@ -2116,7 +2117,7 @@ WebGLTexture::CopyTexSubImage(const char* funcName, TexImageTarget target, GLint
         return;
     auto srcFormat = srcUsage->format;
 
-    if (!ValidateCopyTexImageForFeedback(funcName, level))
+    if (!ValidateCopyTexImageForFeedback(funcName, level, zOffset))
         return;
 
     ////////////////////////////////////