diff --git a/src/CommandDialog.cc b/src/CommandDialog.cc
index 023c22f0..e7773906 100644
--- a/src/CommandDialog.cc
+++ b/src/CommandDialog.cc
@@ -40,7 +40,7 @@ using std::less;
 using std::out_of_range;
 
 CommandDialog::CommandDialog(BScreen &screen, const string &title,
-                             const string precommand) : 
+                             const string &precommand) : 
     TextDialog(screen, title),
     m_precommand(precommand) { }
 
diff --git a/src/CommandDialog.hh b/src/CommandDialog.hh
index 0e12ce34..a976bc43 100644
--- a/src/CommandDialog.hh
+++ b/src/CommandDialog.hh
@@ -35,7 +35,7 @@ class Command;
 class CommandDialog: public TextDialog {
 public:
     CommandDialog(BScreen &screen, const std::string &title,
-                  const std::string pre_command = "");
+                  const std::string &pre_command = "");
 
     /**
      * Sets the command to be executed after the command is done.