diff --git a/src/map/include/winSketch.hpp b/src/map/include/winSketch.hpp
index 7a07bf23..ee02632a 100644
--- a/src/map/include/winSketch.hpp
+++ b/src/map/include/winSketch.hpp
@@ -301,7 +301,11 @@ namespace skch
                     << "[wfmash::mashmap] Filtered " << filtered_kmers << "/" << total_kmers 
                     << " k-mers occurring > " << freq_cutoff << " times"
                     << " (target: " << (param.max_kmer_freq <= 1.0 ? 
-                                      (std::stringstream() << std::fixed << std::setprecision(2) << (param.max_kmer_freq * 100)).str() + "%" :
+                                      ([&]() { 
+                                          std::stringstream ss;
+                                          ss << std::fixed << std::setprecision(2) << (param.max_kmer_freq * 100);
+                                          return ss.str();
+                                      })() + "%" :
                                       ">" + std::to_string((int)param.max_kmer_freq) + " occurrences") 
                     << ")" << std::endl;
         }