diff --git a/goopack/goopack.go b/goopack/goopack.go
index aa83899..1fb477f 100644
--- a/goopack/goopack.go
+++ b/goopack/goopack.go
@@ -398,6 +398,17 @@ func addFlags(args []string) {
 	}
 }
 
+func populateVars() map[string]string {
+	varMap := map[string]string{}
+	flag.Visit(func(flg *flag.Flag) {
+		if strings.HasPrefix(flg.Name, varFlagPrefix) {
+			varMap[strings.TrimPrefix(flg.Name, varFlagPrefix)] = flg.Value.String()
+		}
+	})
+
+	return varMap
+}
+
 func usage() {
 	fmt.Printf("Usage: %s <path/to/goospec>\n", filepath.Base(os.Args[0]))
 }
@@ -431,7 +442,7 @@ func main() {
 		}
 	}
 
-	var varMap map[string]string
+	varMap := populateVars()
 	gs, err := goolib.ReadGooSpec(flag.Arg(0), varMap)
 	if err != nil {
 		log.Fatal(err)
diff --git a/goopack/goopack_test.go b/goopack/goopack_test.go
index a8c318f..599a6ae 100644
--- a/goopack/goopack_test.go
+++ b/goopack/goopack_test.go
@@ -165,6 +165,18 @@ func TestWriteFiles(t *testing.T) {
 	}
 }
 
+func TestPopulateVars(t *testing.T) {
+	flag.String("var:TestPopulateVars1", "", "")
+	flag.String("var:TestPopulateVars2", "", "")
+	flag.CommandLine.Parse([]string{"-var:TestPopulateVars1", "value", "-var:TestPopulateVars2=value"})
+	want := map[string]string{"TestPopulateVars1": "value", "TestPopulateVars2": "value"}
+
+	got := populateVars()
+	if !reflect.DeepEqual(want, got) {
+		t.Errorf("want: %q, got: %q", want, got)
+	}
+}
+
 func TestAddFlags(t *testing.T) {
 	firstFlag := "var:first_var"
 	secondFlag := "var:second_var"