diff --git a/dev/cuda/matmul_backward.cu b/dev/cuda/matmul_backward.cu
index b1d8cff..806bb98 100644
--- a/dev/cuda/matmul_backward.cu
+++ b/dev/cuda/matmul_backward.cu
@@ -71,7 +71,7 @@ void matmul_backward_cpu(float* dinp, float* dweight, float* dbias,
 __global__ void matmul_backward_bias_kernel_naive(float* dbias, const float* dout, int B, int T, int OC) {
     int o = blockIdx.x * blockDim.x + threadIdx.x;
     if (o < OC) {
-        double sum = ;
+        double sum = 0.0;
         for (int b = 0; b < B; b++) {
             for (int t = 0; t < T; t++) {
                 sum += dout[b * T * OC + t * OC + o];