I want to use PCA for feature reduction dimension

I want to use PCA (sklearn.decomposition) for feature reduction dimension.

INPUT: X [200,4096]
and I want to reduce to 400 dimensions
pca = PCA(n_components=400)
pca.fit(X)
newX = pca.transform(X)
but
newX [200,200]
How can I solve this problem?