diff --git a/decode_test.go b/decode_test.go
index 3728fec..b620ce8 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -24,6 +24,9 @@
 package hessian
 
 import (
+	"github.com/apache/dubbo-go-hessian2/java_exception"
+	"github.com/stretchr/testify/assert"
+	"io/ioutil"
 	"log"
 	"os"
 	"os/exec"
@@ -127,3 +130,28 @@
 	}
 	expected(r)
 }
+
+func TestRuntimeException(t *testing.T) {
+	// this byte slice in the file  is generated by java
+	c := getByteFromFile("RuntimeException.txt")
+	decoder := NewDecoder(c)
+	r, err := decoder.Decode()
+	assert.Nil(t, err)
+	_, j := r.(*java_exception.RuntimeException)
+	assert.True(t, j)
+}
+
+func TestBizException(t *testing.T) {
+	// this byte slice in the file  is generated by java
+	c := getByteFromFile("BizDddException.txt")
+	decoder := NewDecoder(c)
+	r, err := decoder.Decode()
+	assert.Nil(t, err)
+	_, j := r.(*UnknownException)
+	assert.True(t, j)
+}
+
+func getByteFromFile(fname string) []byte {
+	c, _ := ioutil.ReadFile("test_resource/" + fname)
+	return c
+}
diff --git a/java_unknown_exception.go b/java_unknown_exception.go
index 45f5a00..6787e3c 100644
--- a/java_unknown_exception.go
+++ b/java_unknown_exception.go
@@ -45,11 +45,11 @@
 	}
 	// if have these 4 fields, it is throwable struct
 	if count == 4 {
+		mutex.Lock()
+		defer mutex.Unlock()
 		if throwable, ok = getStructInfo(cls.javaName); ok {
 			return throwable, true
 		}
-		mutex.Lock()
-		defer mutex.Unlock()
 		RegisterPOJO(newBizException(cls.javaName))
 		if throwable, ok = getStructInfo(cls.javaName); ok {
 			return throwable, true
diff --git a/test_resource/BizDddException.txt b/test_resource/BizDddException.txt
new file mode 100644
index 0000000..f06b585
--- /dev/null
+++ b/test_resource/BizDddException.txt
Binary files differ
diff --git a/test_resource/RuntimeException.txt b/test_resource/RuntimeException.txt
new file mode 100644
index 0000000..430d269
--- /dev/null
+++ b/test_resource/RuntimeException.txt
Binary files differ