diff --git a/LSTM.lua b/LSTM.lua
index 8367adff..6be280c6 100644
--- a/LSTM.lua
+++ b/LSTM.lua
@@ -143,7 +143,7 @@ function layer:updateOutput(input)
     end
   end
 
-  local bias_expand = self.bias:view(1, 4 * H):expand(N, 4 * H)
+  local bias_expand = self.bias:view(1, 4 * H):expand(N * T, 4 * H)
   local Wx = self.weight[{{1, D}}]
   local Wh = self.weight[{{D + 1, D + H}}]
 
@@ -152,12 +152,11 @@ function layer:updateOutput(input)
   c:resize(N, T, H):zero()
   local prev_h, prev_c = h0, c0
   self.gates:resize(N, T, 4 * H):zero()
+  self.gates:view(N * T, 4 * H):addmm(bias_expand, x:view(N * T, D), Wx)
   for t = 1, T do
-    local cur_x = x[{{}, t}]
     local next_h = h[{{}, t}]
     local next_c = c[{{}, t}]
     local cur_gates = self.gates[{{}, t}]
-    cur_gates:addmm(bias_expand, cur_x, Wx)
     cur_gates:addmm(prev_h, Wh)
     cur_gates[{{}, {1, 3 * H}}]:sigmoid()
     cur_gates[{{}, {3 * H + 1, 4 * H}}]:tanh()