diff --git a/common/ParameterRecord.cc b/common/ParameterRecord.cc
index a108e03a6236bf7b17483c4e35db8fe6b149add7..6aa9f90d5fb0d7d1c7e7e008ce09b38313d83c47 100644
--- a/common/ParameterRecord.cc
+++ b/common/ParameterRecord.cc
@@ -13,7 +13,7 @@ namespace common {
 std::ostream& operator<<(std::ostream& os, const ParameterRecord& record) {
   bool first = true;
   os << '{';
-  for (const std::pair<std::string, ParameterValue>& entry : record) {
+  for (const std::pair<const std::string, ParameterValue>& entry : record) {
     if (first) {
       first = false;
     } else {
diff --git a/common/ParameterSet.cc b/common/ParameterSet.cc
index de2c12ec1b2b8454c27f5e5045f0edbaeec7facc..c34770052792290f41dd3426e52c7bcb81473ac5 100644
--- a/common/ParameterSet.cc
+++ b/common/ParameterSet.cc
@@ -71,7 +71,7 @@ blob::BlobOStream& operator<<(blob::BlobOStream& stream,
                               const ParameterSet& set) {
   stream.putStart("ParameterSet", 1);
   stream << static_cast<std::uint32_t>(set.size());
-  for (const std::pair<std::string, ParameterValue>& entry : set) {
+  for (const std::pair<const std::string, ParameterValue>& entry : set) {
     stream << entry.first << entry.second.get();
   }
   stream.putEnd();