diff --git a/.travis.yml b/.travis.yml
index d6064b55..041b45aa 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,8 @@
 language: go
 
+go:
+    - "1.10.x"
+
 install: make deps
 
 script:
@@ -7,4 +10,3 @@ script:
 - tar -xzf goreleaser_Linux_x86_64.tar.gz -C $GOPATH/bin
 - make
 - make test
-- ./.check-gofmt.sh
diff --git a/irc/modes/modes.go b/irc/modes/modes.go
index 287dbd44..310e46f4 100644
--- a/irc/modes/modes.go
+++ b/irc/modes/modes.go
@@ -340,6 +340,10 @@ func NewModeSet() *ModeSet {
 
 // test whether `mode` is set
 func (set *ModeSet) HasMode(mode Mode) bool {
+	if set == nil {
+		return false
+	}
+
 	set.RLock()
 	defer set.RUnlock()
 	return set.modes[mode]
@@ -362,6 +366,10 @@ func (set *ModeSet) SetMode(mode Mode, on bool) (applied bool) {
 
 // return the modes in the set as a slice
 func (set *ModeSet) AllModes() (result []Mode) {
+	if set == nil {
+		return
+	}
+
 	set.RLock()
 	defer set.RUnlock()
 
@@ -372,22 +380,27 @@ func (set *ModeSet) AllModes() (result []Mode) {
 }
 
 // String returns the modes in this set.
-func (set *ModeSet) String() string {
+func (set *ModeSet) String() (result string) {
+	if set == nil {
+		return
+	}
+
 	set.RLock()
 	defer set.RUnlock()
 
-	if len(set.modes) == 0 {
-		return ""
-	}
-	var result []byte
+	var buf strings.Builder
 	for mode := range set.modes {
-		result = append(result, mode.String()...)
+		buf.WriteRune(rune(mode))
 	}
-	return string(result)
+	return buf.String()
 }
 
 // Prefixes returns a list of prefixes for the given set of channel modes.
 func (set *ModeSet) Prefixes(isMultiPrefix bool) (prefixes string) {
+	if set == nil {
+		return
+	}
+
 	set.RLock()
 	defer set.RUnlock()
 
diff --git a/irc/modes/modes_test.go b/irc/modes/modes_test.go
index 8f20bdfc..216add3c 100644
--- a/irc/modes/modes_test.go
+++ b/irc/modes/modes_test.go
@@ -35,3 +35,16 @@ func TestSetMode(t *testing.T) {
 		t.Errorf("unexpected modestring: %s", modeString)
 	}
 }
+
+func TestNilReceivers(t *testing.T) {
+	var set ModeSet
+
+	if set.HasMode(Invisible) {
+		t.Errorf("nil ModeSet should not have any modes")
+	}
+
+	str := set.String()
+	if str != "" {
+		t.Errorf("nil Modeset should have empty String(), got %v instead", str)
+	}
+}