diff --git a/core/src/main/java/com/alibaba/fastjson2/reader/ObjectReaderCreatorASM.java b/core/src/main/java/com/alibaba/fastjson2/reader/ObjectReaderCreatorASM.java
index e3f56883ec..bb8d72af42 100644
--- a/core/src/main/java/com/alibaba/fastjson2/reader/ObjectReaderCreatorASM.java
+++ b/core/src/main/java/com/alibaba/fastjson2/reader/ObjectReaderCreatorASM.java
@@ -400,7 +400,7 @@ public <T> ObjectReader<T> createObjectReader(Class<T> objectClass, Type objectT
                     "(J)Ljava/lang/Object;"
             );
 
-            if (fieldBased && defaultConstructor == null) {
+            if (fieldBased && (defaultConstructor == null || !Modifier.isPublic(defaultConstructor.getModifiers()) || !Modifier.isPublic(objectClass.getModifiers()))) {
                 mw.visitFieldInsn(Opcodes.GETSTATIC, TYPE_UNSAFE_UTILS, "UNSAFE", "Lsun/misc/Unsafe;");
                 mw.visitVarInsn(Opcodes.ALOAD, 0);
                 mw.visitFieldInsn(Opcodes.GETFIELD, TYPE_OBJECT_READER_ADAPTER, "objectClass", "Ljava/lang/Class;");
diff --git a/core/src/test/java/com/alibaba/fastjson2/issues/Issue751.java b/core/src/test/java/com/alibaba/fastjson2/issues/Issue751.java
new file mode 100644
index 0000000000..178060ff02
--- /dev/null
+++ b/core/src/test/java/com/alibaba/fastjson2/issues/Issue751.java
@@ -0,0 +1,34 @@
+package com.alibaba.fastjson2.issues;
+
+import com.alibaba.fastjson2.JSONB;
+import com.alibaba.fastjson2.JSONReader;
+import org.junit.jupiter.api.Test;
+
+import java.io.Serializable;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class Issue751 {
+    @Test
+    public void test() {
+        byte[] bytes = JSONB.toBytes(new Data());
+        Object o = JSONB.parseObject(bytes, Data.class, JSONReader.Feature.FieldBased);
+        assertEquals(Data.class, o.getClass());
+    }
+
+    static class Data
+            implements Serializable {
+        private String mData = "";
+
+        public Data() {
+        }
+
+        public String getData() {
+            return mData;
+        }
+
+        public void setData(String data) {
+            mData = data;
+        }
+    }
+}