Here we study a recently proposed watermarking scheme based on the paper "Wavelet Tree Quantization" (WTQ) by Wang and Lin (IEEE Trans Image Process 13(2): [154][155][156][157][158][159][160][161][162][163][164][165] 2004). In given scheme, wavelet coefficients corresponding to the same spatial locations are grouped together. Two such groups, selected at random, constitute a supertree. Some of these supertrees are quantized to embed the watermark information in the image. In the process of cryptanalysis we first identify the groups which are quantized during the watermark insertion process. Then we select the nonquantized groups and quantize them too, to remove the watermark. Experimental results show that the watermark is completely removed by this attack. The cryptanalysis falls under the cipher text only jamming attack which requires only a single watermarked copy. Further, This is an extended and revised version of the paper we suitably modify the WTQ scheme to make it robust against such cryptanalytic attacks.