diff --git a/cmd/specgen/pkgtmpl.go b/cmd/specgen/pkgtmpl.go
index 4ae708f..e5d56db 100644
--- a/cmd/specgen/pkgtmpl.go
+++ b/cmd/specgen/pkgtmpl.go
@@ -32,18 +32,18 @@ type {{$srvIdent}} struct {
 
 // {{$reqType}} is the XML structure for the input arguments for action {{.Name}}.
 type {{$reqType}} struct {{"{"}}{{range .Arguments}}{{if .IsInput}}
-	{{.Name}} string
+	{{.Name}} {{$srv.SCPD.GoKindNameForVariable .RelatedStateVariable "string"}}
 {{end}}{{end}}}
 
 // {{$respType}} is the XML structure for the output arguments for action {{.Name}}.
 type {{$respType}} struct {{"{"}}{{range .Arguments}}{{if .IsOutput}}
-	{{.Name}} string
+	{{.Name}} {{$srv.SCPD.GoKindNameForVariable .RelatedStateVariable "string"}}
 {{end}}{{end}}}
 
 func (client *{{$srvIdent}}) {{.Name}}({{range .Arguments}}{{if .IsInput}}
-	{{.Name}} string,
+	{{.Name}} {{$srv.SCPD.GoKindNameForVariable .RelatedStateVariable "string"}},
 {{end}}{{end}}) ({{range .Arguments}}{{if .IsOutput}}
-	{{.Name}} string,
+	{{.Name}} {{$srv.SCPD.GoKindNameForVariable .RelatedStateVariable "string"}},
 {{end}}{{end}} err error) {
 	request := {{$reqType}}{
 {{range .Arguments}}{{if .IsInput}}
diff --git a/scpd/scpd.go b/scpd/scpd.go
index c562121..f2e7318 100644
--- a/scpd/scpd.go
+++ b/scpd/scpd.go
@@ -37,6 +37,49 @@ func (scpd *SCPD) Clean() {
 	}
 }
 
+var dataTypeToGoKindName = map[string]string{
+	"ui1":   "byte",
+	"ui2":   "uint16",
+	"ui4":   "uint32",
+	"i1":    "int8",
+	"i2":    "int16",
+	"i4":    "int32",
+	"int":   "int64",
+	"float": "float32",
+	"r4":    "float32",
+	"r8":    "float64",
+	// "fixed.14.4" ~ "float64"
+	"number": "float64",
+	"char":   "string",
+	"string": "string",
+	// "date"
+	// "dateTime"
+	// "dateTime.tz"
+	// "boolean"
+	// "bin.base64"
+	// "bin.hex"
+	// "uri"
+	// "uuid"
+}
+
+// Returns the name of the Go "kind" of type for the named state variable. If
+// the state variable is unknown, returns default_.
+func (scpd *SCPD) GoKindNameForVariable(variable string, default_ string) string {
+	for i := range scpd.StateVariables {
+		v := &scpd.StateVariables[i]
+		if v.Name != variable {
+			continue
+		}
+
+		if kindName, ok := dataTypeToGoKindName[v.DataType.Name]; ok {
+			return kindName
+		} else {
+			return default_
+		}
+	}
+	return default_
+}
+
 // SpecVersion is part of a SCPD document, describes the version of the
 // specification that the data adheres to.
 type SpecVersion struct {