diff --git a/src/Rules.cpp b/src/Rules.cpp
index cc39e6b6..8ba84a26 100644
--- a/src/Rules.cpp
+++ b/src/Rules.cpp
@@ -146,12 +146,14 @@ void Rules::set (const std::string& key, const std::string& value)
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-// Provide a vector of all configuration keys.
-std::vector <std::string> Rules::all () const
+// Provide a vector of all configuration keys. If a stem is provided, only
+// return matching keys.
+std::vector <std::string> Rules::all (const std::string& stem) const
 {
   std::vector <std::string> items;
   for (const auto& it : _settings)
-    items.push_back (it.first);
+    if (stem == "" || it.first.find (stem) == 0)
+      items.push_back (it.first);
 
   return items;
 }
diff --git a/src/Rules.h b/src/Rules.h
index 88d9f782..5766b40b 100644
--- a/src/Rules.h
+++ b/src/Rules.h
@@ -49,7 +49,7 @@ public:
   void set (const std::string&, const double);
   void set (const std::string&, const std::string&);
 
-  std::vector <std::string> all () const;
+  std::vector <std::string> all (const std::string& stem = "") const;
 
   std::string dump () const;