diff --git a/src/c_api.cpp b/src/c_api.cpp
index f0a823c2990e..b67a8748fb39 100644
--- a/src/c_api.cpp
+++ b/src/c_api.cpp
@@ -523,7 +523,7 @@ class Booster {
     for (const auto& name : boosting_->FeatureNames()) {
       if (idx < len) {
         std::memcpy(out_strs[idx], name.c_str(), std::min(name.size() + 1, buffer_len));
-        out_strs[idx][buffer_len-1] = '\0';
+        out_strs[idx][buffer_len - 1] = '\0';
       }
       *out_buffer_len = std::max(name.size() + 1, *out_buffer_len);
       ++idx;