diff --git a/src/stan/io/stan_csv_reader.hpp b/src/stan/io/stan_csv_reader.hpp
index 47c40565f7..1851a814e2 100644
--- a/src/stan/io/stan_csv_reader.hpp
+++ b/src/stan/io/stan_csv_reader.hpp
@@ -219,7 +219,8 @@ class stan_csv_reader {
     return true;
   }
 
-  static bool read_adaptation(std::istream& in, stan_csv_adaptation& adaptation) {
+  static bool read_adaptation(std::istream& in,
+                              stan_csv_adaptation& adaptation) {
     std::stringstream ss;
     std::string line;
     int lines = 0;