diff --git a/pkg/irc/case.go b/pkg/irc/case.go
new file mode 100644
index 00000000..ef24c590
--- /dev/null
+++ b/pkg/irc/case.go
@@ -0,0 +1,125 @@
+package irc
+
+import (
+	"unicode/utf8"
+)
+
+const (
+	// ASCII maps a-z as the lower case of A-Z
+	ASCII = "ascii"
+	// RFC1459 maps a-z and {, |, }, ~ as the lower case of A-Z and [, \, ], ^
+	RFC1459 = "rfc1459"
+	// RFC1459Strict maps a-z and {, |, } as the lower case of A-Z and [, \, ]
+	RFC1459Strict = "strict-rfc1459"
+)
+
+func (c *Client) Casefold(s string) string {
+	mapping := c.Support.Get("CASEMAPPING")
+	if mapping == "" {
+		mapping = RFC1459
+	}
+	return Casefold(mapping, s)
+}
+
+func (c *Client) EqualFold(s1, s2 string) bool {
+	mapping := c.Support.Get("CASEMAPPING")
+	if mapping == "" {
+		mapping = RFC1459
+	}
+	return EqualFold(mapping, s1, s2)
+}
+
+func Casefold(mapping, s string) string {
+	switch mapping {
+	case ASCII:
+		return toLower(s, 'Z')
+	case RFC1459:
+		return toLower(s, '^')
+	case RFC1459Strict:
+		return toLower(s, ']')
+	}
+
+	return s
+}
+
+func EqualFold(mapping, s1, s2 string) bool {
+	switch mapping {
+	case ASCII:
+		return equalFold(s1, s2, 'Z')
+	case RFC1459:
+		return equalFold(s1, s2, '^')
+	case RFC1459Strict:
+		return equalFold(s1, s2, ']')
+	}
+
+	return s1 == s2
+}
+
+func toLower(s string, end byte) string {
+	hasUpper := false
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if hasUpper = 'A' <= c && c <= end; hasUpper {
+			break
+		}
+	}
+
+	if !hasUpper {
+		return s
+	}
+
+	b := make([]byte, len(s))
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+
+		// Skip Unicode characters
+		if c >= utf8.RuneSelf {
+			_, size := utf8.DecodeRuneInString(s[i:])
+			for cEnd := i + size; i < cEnd; i++ {
+				b[i] = s[i]
+			}
+			i--
+			continue
+		}
+
+		if 'A' <= c && c <= end {
+			c += 32
+		}
+		b[i] = c
+	}
+	return string(b)
+}
+
+func equalFold(s1, s2 string, end rune) bool {
+	for s1 != "" && s2 != "" {
+		var r1, r2 rune
+		if s1[0] < utf8.RuneSelf {
+			r1, s1 = rune(s1[0]), s1[1:]
+		} else {
+			r, size := utf8.DecodeRuneInString(s1)
+			r1, s1 = r, s1[size:]
+		}
+		if s2[0] < utf8.RuneSelf {
+			r2, s2 = rune(s2[0]), s2[1:]
+		} else {
+			r, size := utf8.DecodeRuneInString(s2)
+			r2, s2 = r, s2[size:]
+		}
+
+		if r1 == r2 {
+			continue
+		}
+
+		if r2 < r1 {
+			r2, r1 = r1, r2
+		}
+
+		if 'A' <= r1 && r1 <= end && r2 == r1+32 {
+			continue
+		}
+
+		return false
+	}
+
+	return s1 == s2
+}
diff --git a/pkg/irc/case_test.go b/pkg/irc/case_test.go
new file mode 100644
index 00000000..3b8ec857
--- /dev/null
+++ b/pkg/irc/case_test.go
@@ -0,0 +1,27 @@
+package irc
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCasefold(t *testing.T) {
+	assert.Equal(t, "caላke[^", Casefold(ASCII, "CaላkE[^"))
+	assert.Equal(t, "caላke{~", Casefold(RFC1459, "CaላkE[^"))
+	assert.Equal(t, "caላke{^", Casefold(RFC1459Strict, "CaላkE[^"))
+}
+
+func TestEqualFold(t *testing.T) {
+	assert.True(t, EqualFold(ASCII, "caላke[^", "CaላkE[^"))
+	assert.False(t, EqualFold(ASCII, "caላke{~", "CaላkE[^"))
+
+	assert.True(t, EqualFold(RFC1459, "caላke{~", "CaላkE[^"))
+	assert.False(t, EqualFold(RFC1459, "cላke[^", "CaላkE[^"))
+
+	assert.True(t, EqualFold(RFC1459Strict, "caላke{^", "CaላkE[^"))
+	assert.False(t, EqualFold(RFC1459Strict, "caላke[~", "CaላkE[^"))
+
+	assert.True(t, EqualFold(ASCII, "", ""))
+	assert.False(t, EqualFold(ASCII, "", " "))
+}
diff --git a/pkg/irc/conn.go b/pkg/irc/conn.go
index 1708dce9..20c9ac07 100644
--- a/pkg/irc/conn.go
+++ b/pkg/irc/conn.go
@@ -213,12 +213,12 @@ func (c *Client) recv() {
 			go c.write("PONG :" + msg.LastParam())
 
 		case Join:
-			if msg.Nick == c.GetNick() {
+			if c.EqualFold(msg.Nick, c.GetNick()) {
 				c.addChannel(msg.Params[0])
 			}
 
 		case Nick:
-			if msg.Nick == c.GetNick() {
+			if c.EqualFold(msg.Nick, c.GetNick()) {
 				c.setNick(msg.LastParam())
 			}
 
diff --git a/pkg/irc/message.go b/pkg/irc/message.go
index da109d41..2da60ff3 100644
--- a/pkg/irc/message.go
+++ b/pkg/irc/message.go
@@ -140,9 +140,9 @@ func (i *iSupport) Get(key string) string {
 
 func (i *iSupport) GetInt(key string) int {
 	i.lock.Lock()
-	v := cast.ToInt(i.support[key])
+	v := i.support[key]
 	i.lock.Unlock()
-	return v
+	return cast.ToInt(v)
 }
 
 func splitParam(param string) (string, string) {