--- a/dom/canvas/WebGLTextureUpload.cpp
+++ b/dom/canvas/WebGLTextureUpload.cpp
@@ -439,16 +439,21 @@ WebGLTexture::TexSubImage(const char* fu
 {
     const GLint border = 0;
     dom::RootedTypedArray<dom::Uint8ClampedArray> scopedArr(dom::RootingCx());
     const auto blob = ValidateTexOrSubImage(mContext, funcName, target, width, height,
                                             depth, border, pi, src, &scopedArr);
     if (!blob)
         return;
 
+    if (!blob->HasData()) {
+        mContext->ErrorInvalidValue("%s: Source must not be null.", funcName);
+        return;
+    }
+
     TexSubImage(funcName, target, level, xOffset, yOffset, zOffset, pi, blob.get());
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////
 //////////////////////////////////////////////////////////////////////////////////////////
 
 static bool
 ValidateTexImage(WebGLContext* webgl, WebGLTexture* texture, const char* funcName,