diff --git a/opts/hosts_unix.go b/opts/hosts_unix.go
new file mode 100644
index 0000000000..a29335e605
--- /dev/null
+++ b/opts/hosts_unix.go
@@ -0,0 +1,7 @@
+// +build !windows
+
+package opts
+
+import "fmt"
+
+var DefaultHost = fmt.Sprintf("unix://%s", DefaultUnixSocket)
diff --git a/opts/hosts_windows.go b/opts/hosts_windows.go
new file mode 100644
index 0000000000..55eac2aaca
--- /dev/null
+++ b/opts/hosts_windows.go
@@ -0,0 +1,7 @@
+// +build windows
+
+package opts
+
+import "fmt"
+
+var DefaultHost = fmt.Sprintf("tcp://%s:%d", DefaultHTTPHost, DefaultHTTPPort)
diff --git a/opts/opts.go b/opts/opts.go
index b739012791..6d1b2f7b99 100644
--- a/opts/opts.go
+++ b/opts/opts.go
@@ -32,37 +32,37 @@ var (
 // ListVar Defines a flag with the specified names and usage, and put the value
 // list into ListOpts that will hold the values.
 func ListVar(values *[]string, names []string, usage string) {
-	flag.Var(newListOptsRef(values, nil), names, usage)
+	flag.Var(NewListOptsRef(values, nil), names, usage)
 }
 
 // MapVar Defines a flag with the specified names and usage, and put the value
 // map into MapOpt that will hold the values (key,value).
 func MapVar(values map[string]string, names []string, usage string) {
-	flag.Var(newMapOpt(values, nil), names, usage)
+	flag.Var(NewMapOpts(values, nil), names, usage)
 }
 
 // LogOptsVar Defines a flag with the specified names and usage for --log-opts,
 // and put the value map into MapOpt that will hold the values (key,value).
 func LogOptsVar(values map[string]string, names []string, usage string) {
-	flag.Var(newMapOpt(values, nil), names, usage)
+	flag.Var(NewMapOpts(values, nil), names, usage)
 }
 
 // HostListVar Defines a flag with the specified names and usage and put the
 // value into a ListOpts that will hold the values, validating the Host format.
 func HostListVar(values *[]string, names []string, usage string) {
-	flag.Var(newListOptsRef(values, ValidateHost), names, usage)
+	flag.Var(NewListOptsRef(values, ValidateHost), names, usage)
 }
 
 // IPListVar Defines a flag with the specified names and usage and put the
 // value into a ListOpts that will hold the values, validating the IP format.
 func IPListVar(values *[]string, names []string, usage string) {
-	flag.Var(newListOptsRef(values, ValidateIPAddress), names, usage)
+	flag.Var(NewListOptsRef(values, ValidateIPAddress), names, usage)
 }
 
 // DNSSearchListVar Defines a flag with the specified names and usage and put the
 // value into a ListOpts that will hold the values, validating the DNS search format.
 func DNSSearchListVar(values *[]string, names []string, usage string) {
-	flag.Var(newListOptsRef(values, ValidateDNSSearch), names, usage)
+	flag.Var(NewListOptsRef(values, ValidateDNSSearch), names, usage)
 }
 
 // IPVar Defines a flag with the specified names and usage for IP and will use
@@ -74,12 +74,12 @@ func IPVar(value *net.IP, names []string, defaultValue, usage string) {
 // LabelListVar Defines a flag with the specified names and usage and put the
 // value into a ListOpts that will hold the values, validating the label format.
 func LabelListVar(values *[]string, names []string, usage string) {
-	flag.Var(newListOptsRef(values, ValidateLabel), names, usage)
+	flag.Var(NewListOptsRef(values, ValidateLabel), names, usage)
 }
 
 // UlimitMapVar Defines a flag with the specified names and usage for --ulimit,
 // and put the value map into a UlimitOpt that will hold the values.
-func UlimitMapVar(values map[string]*ulimit.Ulimit, names []string, usage string) {
+func UlimitMapVar(values *map[string]*ulimit.Ulimit, names []string, usage string) {
 	flag.Var(NewUlimitOpt(values), names, usage)
 }
 
@@ -92,10 +92,10 @@ type ListOpts struct {
 // NewListOpts Create a new ListOpts with the specified validator.
 func NewListOpts(validator ValidatorFctType) ListOpts {
 	var values []string
-	return *newListOptsRef(&values, validator)
+	return *NewListOptsRef(&values, validator)
 }
 
-func newListOptsRef(values *[]string, validator ValidatorFctType) *ListOpts {
+func NewListOptsRef(values *[]string, validator ValidatorFctType) *ListOpts {
 	return &ListOpts{
 		values:    values,
 		validator: validator,
@@ -191,7 +191,10 @@ func (opts *MapOpts) String() string {
 	return fmt.Sprintf("%v", map[string]string((opts.values)))
 }
 
-func newMapOpt(values map[string]string, validator ValidatorFctType) *MapOpts {
+func NewMapOpts(values map[string]string, validator ValidatorFctType) *MapOpts {
+	if values == nil {
+		values = make(map[string]string)
+	}
 	return &MapOpts{
 		values:    values,
 		validator: validator,
diff --git a/opts/opts_test.go b/opts/opts_test.go
index 3e639c1fa0..f08df30be6 100644
--- a/opts/opts_test.go
+++ b/opts/opts_test.go
@@ -32,7 +32,7 @@ func TestValidateIPAddress(t *testing.T) {
 
 func TestMapOpts(t *testing.T) {
 	tmpMap := make(map[string]string)
-	o := newMapOpt(tmpMap, logOptsValidator)
+	o := NewMapOpts(tmpMap, logOptsValidator)
 	o.Set("max-size=1")
 	if o.String() != "map[max-size:1]" {
 		t.Errorf("%s != [map[max-size:1]", o.String())
diff --git a/opts/ulimit.go b/opts/ulimit.go
index 361eadf220..f8d34365f5 100644
--- a/opts/ulimit.go
+++ b/opts/ulimit.go
@@ -7,10 +7,13 @@ import (
 )
 
 type UlimitOpt struct {
-	values map[string]*ulimit.Ulimit
+	values *map[string]*ulimit.Ulimit
 }
 
-func NewUlimitOpt(ref map[string]*ulimit.Ulimit) *UlimitOpt {
+func NewUlimitOpt(ref *map[string]*ulimit.Ulimit) *UlimitOpt {
+	if ref == nil {
+		ref = &map[string]*ulimit.Ulimit{}
+	}
 	return &UlimitOpt{ref}
 }
 
@@ -20,14 +23,14 @@ func (o *UlimitOpt) Set(val string) error {
 		return err
 	}
 
-	o.values[l.Name] = l
+	(*o.values)[l.Name] = l
 
 	return nil
 }
 
 func (o *UlimitOpt) String() string {
 	var out []string
-	for _, v := range o.values {
+	for _, v := range *o.values {
 		out = append(out, v.String())
 	}
 
@@ -36,7 +39,7 @@ func (o *UlimitOpt) String() string {
 
 func (o *UlimitOpt) GetList() []*ulimit.Ulimit {
 	var ulimits []*ulimit.Ulimit
-	for _, v := range o.values {
+	for _, v := range *o.values {
 		ulimits = append(ulimits, v)
 	}