diff --git a/design.txt b/design.txt
index 855b7ff3..e4a13c3d 100644
--- a/design.txt
+++ b/design.txt
@@ -415,7 +415,7 @@ Filter: (lib/filter.cpp)
 		substrings, so take the intersection of all sets returned by
 		the filter_index for a given substring.
 
-	const std::string & filter :: to_lowercase(const std::string &string);
+	std::string filter :: to_lowercase(const std::string &string);
 		Split the string into words following step 1 of "Parsing"
 		(above).  Assemble and return a result string using the lower
 		case cache to convert each term to lowercase.
diff --git a/design/filter.txt b/design/filter.txt
index 4f7100b9..45243582 100644
--- a/design/filter.txt
+++ b/design/filter.txt
@@ -44,7 +44,7 @@ Filter: (lib/filter.cpp)
 		substrings, so take the intersection of all sets returned by
 		the filter_index for a given substring.
 
-	const std::string & filter :: to_lowercase(const std::string &string);
+	std::string filter :: to_lowercase(const std::string &string);
 		Split the string into words following step 1 of "Parsing"
 		(above).  Assemble and return a result string using the lower
 		case cache to convert each term to lowercase.
diff --git a/include/filter.h b/include/filter.h
index 674fdaf2..a88e4dd1 100644
--- a/include/filter.h
+++ b/include/filter.h
@@ -11,11 +11,12 @@ namespace filter {
 
 	void add(const std::string &, unsigned int);
 	void search(const std::string &, std::set<unsigned int> &);
+	std::string to_lowercase(const std::string &);
 
 	void print_cache_stats();
 
 #ifdef CONFIG_TEST
-	Database<IndexEntry, const std::string> &get_index();
+	Database<IndexEntry> &get_index();
 #endif /* CONFIG_TEST */
 
 };
diff --git a/lib/filter.cpp b/lib/filter.cpp
index 3f8b49f7..2f4a57ea 100644
--- a/lib/filter.cpp
+++ b/lib/filter.cpp
@@ -10,7 +10,7 @@
 #include <map>
 #include <set>
 
-static Database<IndexEntry, const std::string> filter_index("");
+static Database<IndexEntry> filter_index("");
 static std::map<std::string, std::string> lowercase_cache;
 static unsigned int lowercase_cache_hits = 0;
 
@@ -136,6 +136,22 @@ void filter :: search(const std::string &text, std::set<unsigned int> &res)
 		find_intersection(*it, res);
 }
 
+std::string filter :: to_lowercase(const std::string &text)
+{
+	std::string res = "";
+	std::list<std::string> parsed;
+	std::list<std::string>::iterator it;
+
+	parse_text(text, parsed);
+	for (it = parsed.begin(); it != parsed.end(); it++) {
+		if (it != parsed.begin())
+			res += " ";
+		res += *it;
+	}
+
+	return res;
+}
+
 void filter :: print_cache_stats()
 {
 	print("Lowercase cache size: %u\n", lowercase_cache.size());
@@ -143,7 +159,7 @@ void filter :: print_cache_stats()
 }
 
 #ifdef CONFIG_TEST
-Database<IndexEntry, const std::string> &filter :: get_index()
+Database<IndexEntry> &filter :: get_index()
 {
 	return filter_index;
 }
diff --git a/tests/filter/filter.cpp b/tests/filter/filter.cpp
index 0a9f30ff..015e1670 100644
--- a/tests/filter/filter.cpp
+++ b/tests/filter/filter.cpp
@@ -48,11 +48,11 @@ std::string quotes [] = {
 
 static const unsigned int num_quotes = sizeof(quotes) / sizeof(std::string);
 
-void print_index(Database<IndexEntry, const std::string> &db)
+void print_index(Database<IndexEntry> &db)
 {
 	db.print_keys();
 	for (unsigned int i = db.first(); i <= db.last(); i = db.next(i)) {
-		print("index[%s] = ", db[i].primary_key().c_str());
+		print("index[%s] = ", db[i].primary_key.c_str());
 		db[i].print();
 		print("\n");
 	}
@@ -74,6 +74,12 @@ void test_search(const std::string &text)
 	print("\n");
 }
 
+void test_lowercase(const std::string &text)
+{
+	std::string res = filter :: to_lowercase(text);
+	print("Lowercasing: \"%s\" returned: \"%s\"\n", text.c_str(), res.c_str());
+}
+
 void test_0()
 {
 	for (unsigned int i = 0; i < num_quotes; i++)
@@ -96,12 +102,30 @@ void test_1()
 	test_search("Th/i-eVEn");
 	test_search("whoops");
 	filter :: print_cache_stats();
+	print("\n");
+}
+
+void test_2()
+{
+	test_lowercase("");
+	test_lowercase("Rincewind");
+	test_lowercase("Rincewind Twoflower Luggage");
+	test_lowercase("the");
+	test_lowercase("the is");
+	test_lowercase("THE IS");
+	test_lowercase("th i");
+	test_lowercase("th i even");
+	test_lowercase("Th/i-eVen");
+	test_lowercase("whoops");
+	test_lowercase("WHOOPS");
+	filter :: print_cache_stats();
 }
 
 int main(int argc, char **argv)
 {
 	test_0();
 	test_1();
+	test_2();
 
 	return 0;
 }
diff --git a/tests/filter/filter.good b/tests/filter/filter.good
index 3c4f9a7e..a2681624 100644
--- a/tests/filter/filter.good
+++ b/tests/filter/filter.good
@@ -741,3 +741,17 @@ Search for: "whoops" returned 1 matches:
 
 Lowercase cache size: 269
 Lowercase cache hits: 121
+
+Lowercasing: "" returned: ""
+Lowercasing: "Rincewind" returned: "rincewind"
+Lowercasing: "Rincewind Twoflower Luggage" returned: "rincewind twoflower luggage"
+Lowercasing: "the" returned: "the"
+Lowercasing: "the is" returned: "the is"
+Lowercasing: "THE IS" returned: "the is"
+Lowercasing: "th i" returned: "th i"
+Lowercasing: "th i even" returned: "th i even"
+Lowercasing: "Th/i-eVen" returned: "th i even"
+Lowercasing: "whoops" returned: "whoops"
+Lowercasing: "WHOOPS" returned: "whoops"
+Lowercase cache size: 271
+Lowercase cache hits: 138