diff --git a/src/common.c b/src/common.c
index fecaa92..eb69b80 100644
--- a/src/common.c
+++ b/src/common.c
@@ -578,10 +578,9 @@ struct str_map
 	size_t len;                         ///< Number of entries in the table
 	void (*free) (void *);              ///< Callback to destruct the payload
 
-	/// Callback to compare keys for equivalence
-	// FIXME: they may still end up on a different index, and actually should;
-	//   delete this callback and put strxfrm() in its place
-	int (*key_cmp) (const char *, const char *);
+	/// Callback that transforms all key values for storage and comparison;
+	/// has to behave exactly like strxfrm().
+	size_t (*key_xfrm) (char *dest, const char *src, size_t n);
 };
 
 // As long as you don't remove the current entry, you can modify the map.
@@ -604,7 +603,7 @@ str_map_init (struct str_map *self)
 	self->alloc = STR_MAP_MIN_ALLOC;
 	self->len = 0;
 	self->free = NULL;
-	self->key_cmp = strcmp;
+	self->key_xfrm = NULL;
 	self->map = xcalloc (self->alloc, sizeof *self->map);
 }
 
@@ -698,13 +697,13 @@ str_map_resize (struct str_map *self, size_t new_size)
 }
 
 static void
-str_map_set (struct str_map *self, const char *key, void *value)
+str_map_set_real (struct str_map *self, const char *key, void *value)
 {
 	uint64_t pos = str_map_pos (self, key);
 	struct str_map_link *iter = self->map[pos];
 	for (; iter; iter = iter->next)
 	{
-		if (self->key_cmp (key, iter->key))
+		if (strcmp (key, iter->key))
 			continue;
 
 		// Storing the same data doesn't destroy it
@@ -748,16 +747,40 @@ str_map_set (struct str_map *self, const char *key, void *value)
 	self->len++;
 }
 
+static void
+str_map_set (struct str_map *self, const char *key, void *value)
+{
+	if (!self->key_xfrm)
+	{
+		str_map_set_real (self, key, value);
+		return;
+	}
+	char tmp[self->key_xfrm (NULL, key, 0) + 1];
+	self->key_xfrm (tmp, key, sizeof tmp);
+	str_map_set_real (self, tmp, value);
+}
+
 static void *
-str_map_find (struct str_map *self, const char *key)
+str_map_find_real (struct str_map *self, const char *key)
 {
 	struct str_map_link *iter = self->map[str_map_pos (self, key)];
 	for (; iter; iter = iter->next)
-		if (!self->key_cmp (key, (const char *) iter + sizeof *iter))
+		if (!strcmp (key, (const char *) iter + sizeof *iter))
 			return iter->data;
 	return NULL;
 }
 
+static void *
+str_map_find (struct str_map *self, const char *key)
+{
+	if (!self->key_xfrm)
+		return str_map_find_real (self, key);
+
+	char tmp[self->key_xfrm (NULL, key, 0) + 1];
+	self->key_xfrm (tmp, key, sizeof tmp);
+	return str_map_find_real (self, tmp);
+}
+
 // --- File descriptor utilities -----------------------------------------------
 
 static void
@@ -1727,7 +1750,7 @@ irc_process_buffer (struct str *buf,
 }
 
 static int
-irc_tolower (char c)
+irc_tolower (int c)
 {
 	if (c == '[')   return '{';
 	if (c == ']')   return '}';
@@ -1736,6 +1759,15 @@ irc_tolower (char c)
 	return c >= 'A' && c <= 'Z' ? c + ('a' - 'A') : c;
 }
 
+static size_t
+irc_strxfrm (char *dest, const char *src, size_t n)
+{
+	size_t len = strlen (src);
+	while (n-- && (*dest++ = irc_tolower (*src++)))
+		;
+	return len;
+}
+
 static int
 irc_strcmp (const char *a, const char *b)
 {
diff --git a/src/kike.c b/src/kike.c
index 0325e41..207ff76 100644
--- a/src/kike.c
+++ b/src/kike.c
@@ -378,12 +378,12 @@ server_context_init (struct server_context *self)
 
 	self->server_name = NULL;
 	str_map_init (&self->users);
-	self->users.key_cmp = irc_strcmp;
+	self->users.key_xfrm = irc_strxfrm;
 	// TODO: set channel_free() as the free function?
 	str_map_init (&self->channels);
-	self->channels.key_cmp = irc_strcmp;
+	self->channels.key_xfrm = irc_strxfrm;
 	str_map_init (&self->handlers);
-	self->handlers.key_cmp = irc_strcmp;
+	self->handlers.key_xfrm = irc_strxfrm;
 
 	poller_init (&self->poller);
 	self->quitting = false;