diff --git a/gen/elem.go b/gen/elem.go
index b8b821ab..6d5d56c6 100644
--- a/gen/elem.go
+++ b/gen/elem.go
@@ -264,6 +264,7 @@ type Map struct {
 	Validx     string // value variable name
 	Value      Elem   // value element
 	isAllowNil bool
+	KeyType string // key type
 }
 
 func (m *Map) SetVarname(s string) {
@@ -284,7 +285,7 @@ func (m *Map) TypeName() string {
 	if m.common.alias != "" {
 		return m.common.alias
 	}
-	m.common.Alias("map[string]" + m.Value.TypeName())
+	m.common.Alias(fmt.Sprintf("map[%s]%s", m.KeyType, m.Value.TypeName()))
 	return m.common.alias
 }
 
@@ -308,6 +309,30 @@ func (m *Map) AllowNil() bool { return true }
 // SetIsAllowNil sets whether the map is allowed to be nil.
 func (m *Map) SetIsAllowNil(b bool) { m.isAllowNil = b }
 
+func (m *Map) KeyStringExpr() string {
+	if m.KeyType == "string" {
+		return m.Keyidx
+	} else {
+		return fmt.Sprintf("%s.MsgpStrMapKey()", m.Keyidx)
+	}
+}
+
+func (m *Map) KeyOrigTypeExpr() string {
+	if m.KeyType == "string" {
+		return m.Keyidx
+	} else {
+		return fmt.Sprintf("*(new(%s).MsgpFromStrMapKey(%s)).(*%s)", m.KeyType, m.Keyidx, m.KeyType)
+	}
+}
+
+func (m *Map) KeySizeExpr() string {
+	if m.KeyType == "string" {
+		return fmt.Sprintf("len(%s)", m.Keyidx)
+	} else {
+		return fmt.Sprintf("%s.MsgpStrMapKeySize()", m.Keyidx)
+	}
+}
+
 type Slice struct {
 	common
 	Index      string
diff --git a/gen/encode.go b/gen/encode.go
index 900c847b..3369b08d 100644
--- a/gen/encode.go
+++ b/gen/encode.go
@@ -229,7 +229,7 @@ func (e *encodeGen) gMap(m *Map) {
 	e.writeAndCheck(mapHeader, lenAsUint32, vname)
 
 	e.p.printf("\nfor %s, %s := range %s {", m.Keyidx, m.Validx, vname)
-	e.writeAndCheck(stringTyp, literalFmt, m.Keyidx)
+	e.writeAndCheck(stringTyp, literalFmt, m.KeyStringExpr())
 	e.ctx.PushVar(m.Keyidx)
 	next(e, m.Value)
 	e.ctx.Pop()
diff --git a/gen/marshal.go b/gen/marshal.go
index 66f280eb..d440099b 100644
--- a/gen/marshal.go
+++ b/gen/marshal.go
@@ -233,7 +233,7 @@ func (m *marshalGen) gMap(s *Map) {
 	vname := s.Varname()
 	m.rawAppend(mapHeader, lenAsUint32, vname)
 	m.p.printf("\nfor %s, %s := range %s {", s.Keyidx, s.Validx, vname)
-	m.rawAppend(stringTyp, literalFmt, s.Keyidx)
+	m.rawAppend(stringTyp, literalFmt, s.KeyStringExpr())
 	m.ctx.PushVar(s.Keyidx)
 	next(m, s.Value)
 	m.ctx.Pop()
diff --git a/gen/size.go b/gen/size.go
index e96e0319..31e33e1a 100644
--- a/gen/size.go
+++ b/gen/size.go
@@ -176,7 +176,7 @@ func (s *sizeGen) gMap(m *Map) {
 	s.p.printf("\nif %s != nil {", vn)
 	s.p.printf("\nfor %s, %s := range %s {", m.Keyidx, m.Validx, vn)
 	s.p.printf("\n_ = %s", m.Validx) // we may not use the value
-	s.p.printf("\ns += msgp.StringPrefixSize + len(%s)", m.Keyidx)
+	s.p.printf("\ns += msgp.StringPrefixSize + %s", m.KeySizeExpr())
 	s.state = expr
 	s.ctx.PushVar(m.Keyidx)
 	next(s, m.Value)
diff --git a/gen/spec.go b/gen/spec.go
index bd57743c..3d6e04c6 100644
--- a/gen/spec.go
+++ b/gen/spec.go
@@ -341,7 +341,7 @@ func (p *printer) mapAssign(m *Map) {
 	if !p.ok() {
 		return
 	}
-	p.printf("\n%s[%s] = %s", m.Varname(), m.Keyidx, m.Validx)
+	p.printf("\n%s[%s] = %s", m.Varname(), m.KeyOrigTypeExpr(), m.Validx)
 }
 
 // clear map keys
diff --git a/msgp/non_str_map_key.go b/msgp/non_str_map_key.go
new file mode 100644
index 00000000..3dd7f7b7
--- /dev/null
+++ b/msgp/non_str_map_key.go
@@ -0,0 +1,10 @@
+package msgp
+
+// NonStrMapKey must be implemented to allow non-string Go types to be used as MessagePack map keys.
+// Msgp maps must have string keys for JSON interop.
+// NonStrMapKey enables conversion from type to string and vice versa.
+type NonStrMapKey interface {
+	MsgpStrMapKey() string
+	MsgpFromStrMapKey(s string) NonStrMapKey
+	MsgpStrMapKeySize() int
+}
diff --git a/parse/getast.go b/parse/getast.go
index 8bb8a8f5..f96f0454 100644
--- a/parse/getast.go
+++ b/parse/getast.go
@@ -479,9 +479,14 @@ func (fs *FileSet) parseExpr(e ast.Expr) gen.Elem {
 	switch e := e.(type) {
 
 	case *ast.MapType:
-		if k, ok := e.Key.(*ast.Ident); ok && k.Name == "string" {
+		switch k := e.Key.(type) {
+		case *ast.Ident:
 			if in := fs.parseExpr(e.Value); in != nil {
-				return &gen.Map{Value: in}
+				return &gen.Map{Value: in, KeyType: k.Name}
+			}
+		case *ast.SelectorExpr:
+			if in := fs.parseExpr(e.Value); in != nil {
+				return &gen.Map{Value: in, KeyType: stringify(k)}
 			}
 		}
 		return nil
diff --git a/printer/print.go b/printer/print.go
index b4ea8217..475fd5f2 100644
--- a/printer/print.go
+++ b/printer/print.go
@@ -94,6 +94,9 @@ func generate(f *parse.FileSet, mode gen.Method) (*bytes.Buffer, *bytes.Buffer,
 	dedup := dedupImports(myImports)
 	writeImportHeader(outbuf, dedup...)
 
+	nonStrMapKeyImpls := nonStrMapKeyImpls(f)
+	writeInterfaceTypeConstraints(outbuf, "msgp.NonStrMapKey", nonStrMapKeyImpls)
+
 	var testbuf *bytes.Buffer
 	var testwr io.Writer
 	if mode&gen.Test == gen.Test {
@@ -131,3 +134,29 @@ func writeImportHeader(b *bytes.Buffer, imports ...string) {
 	}
 	b.WriteString(")\n\n")
 }
+
+func nonStrMapKeyImpls(f *parse.FileSet) []string {
+	m := map[string]struct{}{}
+	for _, identity := range f.Identities {
+		if _struct, ok := identity.(*gen.Struct); ok {
+			for _, field := range _struct.Fields {
+				if _map, ok := field.FieldElem.(*gen.Map); ok {
+					if _map.KeyType != "string" {
+						m[_map.KeyType] = struct{}{}
+					}
+				}
+			}
+		}
+	}
+	r := []string{}
+	for k := range m {
+		r = append(r, k)
+	}
+	return r
+}
+
+func writeInterfaceTypeConstraints(b *bytes.Buffer, _interface string, impls []string) {
+	for _, impl := range impls {
+		fmt.Fprintf(b, "var _ %s = new(%s)\n", _interface, impl)
+	}
+}