diff --git a/ctcdecode/src/decoder_utils.cpp b/ctcdecode/src/decoder_utils.cpp
index 2a35fe48..d37493ed 100644
--- a/ctcdecode/src/decoder_utils.cpp
+++ b/ctcdecode/src/decoder_utils.cpp
@@ -23,12 +23,12 @@ std::vector<std::pair<size_t, float>> get_pruned_log_probs(
     std::sort(
         prob_idx.begin(), prob_idx.end(), pair_comp_second_rev<int, double>);
     if (log_cutoff_prob < 0.0) {
-      double cum_prob = 0.0;
-      cutoff_len = 0;
-      for (size_t i = 0; i < prob_idx.size(); ++i) {
+      double cum_prob = log_input ? prob_idx[0].second : log(prob_idx[0].second);
+      cutoff_len = 1;
+      for (size_t i = 1; i < prob_idx.size(); ++i) {
+        if (cum_prob >= log_cutoff_prob || cutoff_len >= cutoff_top_n) break;
         cum_prob = log_sum_exp(cum_prob, log_input ? prob_idx[i].second : log(prob_idx[i].second) );
         cutoff_len += 1;
-        if (cum_prob >= cutoff_prob || cutoff_len >= cutoff_top_n) break;
       }
     }else{
       cutoff_len = cutoff_top_n;