diff --git a/state/tracker.go b/state/tracker.go
index 978be2a..80de101 100644
--- a/state/tracker.go
+++ b/state/tracker.go
@@ -64,9 +64,13 @@ func (st *stateTracker) GetNick(n string) *Nick {
 // under a "neu" nick rather than the old one.
 func (st *stateTracker) ReNick(old, neu string) {
 	if n, ok := st.nicks[old]; ok {
-		st.nicks[old] = nil, false
-		n.Nick = neu
-		st.nicks[neu] = n
+		if _, ok := st.nicks[neu]; !ok {
+			st.nicks[old] = nil, false
+			n.Nick = neu
+			st.nicks[neu] = n
+		} else {
+			logging.Warn("StateTracker.ReNick(): %s already exists.", neu)
+		}
 	} else {
 		logging.Warn("StateTracker.ReNick(): %s not tracked.", old)
 	}
diff --git a/state/tracker_test.go b/state/tracker_test.go
index 9834144..9bc6368 100644
--- a/state/tracker_test.go
+++ b/state/tracker_test.go
@@ -57,6 +57,45 @@ func TestReNick(t *testing.T) {
 		t.Errorf("Nick test2 doesn't exist after ReNick.")
 	}
 	if len(st.nicks) != 1 {
-		t.Errorf("Nick list changed size during GetNick.")
+		t.Errorf("Nick list changed size during ReNick.")
+	}
+
+	test2 := &Nick{Nick: "test2", st: st}
+	st.nicks["test1"] = test2
+
+	st.ReNick("test1", "test2")
+	if n, ok := st.nicks["test2"]; !ok || n != test1 {
+		t.Errorf("Nick test2 overwritten/deleted by ReNick.")
+	}
+	if n, ok := st.nicks["test1"]; !ok || n != test2 {
+		t.Errorf("Nick test1 overwritten/deleted by ReNick.")
+	}
+	if len(st.nicks) != 2 {
+		t.Errorf("Nick list changed size during ReNick.")
+	}
+
+}
+
+func TestDelNick(t *testing.T) {
+	st := NewTracker()
+
+	test1 := &Nick{Nick: "test1", st: st}
+	st.nicks["test1"] = test1
+
+	st.DelNick("test1")
+
+	if _, ok := st.nicks["test1"]; ok {
+		t.Errorf("Nick test1 still exists after DelNick.")
+	}
+	if len(st.nicks) != 0 {
+		t.Errorf("Nick list still contains nicks after DelNick.")
+	}
+
+	st.nicks["test1"] = test1
+
+	st.DelNick("test2")
+
+	if len(st.nicks) != 1 {
+		t.Errorf("DelNick had unexpected side-effects.")
 	}
 }