diff --git a/lgensemble_io.go b/lgensemble_io.go
index c25aa45..a7b8cc2 100644
--- a/lgensemble_io.go
+++ b/lgensemble_io.go
@@ -298,11 +298,10 @@ func LGEnsembleFromReader(reader *bufio.Reader, loadTransformation bool) (*Ensem
 		return nil, err
 	}
 
-	if err := params.Compare("version", "v2"); err != nil {
-		if err := params.Compare("version", "v3"); err != nil {
-			return nil, err
-		}
+	if err := params.CompareAll("version", []string{"v2", "v3", "v4"}); err != nil {
+		return nil, err
 	}
+
 	nClasses, err := params.ToInt("num_class")
 	if err != nil {
 		return nil, err
diff --git a/util/util.go b/util/util.go
index 5aa0081..0acdac9 100644
--- a/util/util.go
+++ b/util/util.go
@@ -95,6 +95,20 @@ func (p *stringParams) Compare(key string, rhs string) error {
 	return nil
 }
 
+func (p *stringParams) CompareAll(key string, values []string) error {
+	valueStr, isFound := (*p)[key]
+	if !isFound {
+		return fmt.Errorf("no %s field", key)
+	}
+
+	for _, v := range values {
+		if valueStr == v {
+			return nil
+		}
+	}
+	return fmt.Errorf("only %v are supported for %s, got %s", values, key, valueStr)
+}
+
 func (p *stringParams) ToStrSlice(key string) ([]string, error) {
 	valueStr, isFound := (*p)[key]
 	if !isFound {
@@ -267,7 +281,7 @@ func SoftmaxFloat64Slice(rawValues []float64, outputValues []float64, startIndex
 	}
 	if sum != 0.0 {
 		inv_sum := 1.0 / sum
-		for i := startIndex; i < startIndex + len(rawValues); i++ {
+		for i := startIndex; i < startIndex+len(rawValues); i++ {
 			outputValues[i] *= inv_sum
 		}
 	}