diff --git a/src/insets/InsetCommandParams.cpp b/src/insets/InsetCommandParams.cpp
index a0d02e2245..6701c20d5f 100644
--- a/src/insets/InsetCommandParams.cpp
+++ b/src/insets/InsetCommandParams.cpp
@@ -99,7 +99,7 @@ static ParamInfo const & findInfo(InsetCode code, string const & cmdName)
 
 ParamInfo::ParamData::ParamData(std::string const & s, ParamType t,
                                 ParamHandling h, bool ignore,
-                                docstring default_value)
+                                docstring const & default_value)
 	: name_(s), type_(t), handling_(h), ignore_(ignore),
 	  default_value_(default_value)
 {}
diff --git a/src/insets/InsetCommandParams.h b/src/insets/InsetCommandParams.h
index 5f463454c0..2faaf3f545 100644
--- a/src/insets/InsetCommandParams.h
+++ b/src/insets/InsetCommandParams.h
@@ -55,7 +55,7 @@ public:
 		///
 		ParamData(std::string const &, ParamType, ParamHandling = HANDLING_NONE,
 		          bool ignore = false,
-		          docstring default_value = docstring());
+		          docstring const & default_value = docstring());
 		///
 		std::string name() const { return name_; }
 		///