diff --git a/include/smbios_mdrv2.hpp b/include/smbios_mdrv2.hpp
index e53d709..a307332 100644
--- a/include/smbios_mdrv2.hpp
+++ b/include/smbios_mdrv2.hpp
@@ -222,18 +222,24 @@
     uint16_t limit = mdrSMBIOSSize; // set a limit to avoid endless loop
 
     char* target = reinterpret_cast<char*>(dataIn + structLen);
+    if (target == nullptr)
+    {
+        return "";
+    }
     for (uint8_t index = 1; index < positionNum; index++)
     {
         for (; *target != '\0'; target++)
         {
             limit--;
-            if (limit < 1)
+            // When target = dataIn + structLen + limit,
+            // following target++ will be nullptr
+            if (limit < 1 || target == nullptr)
             {
                 return "";
             }
         }
         target++;
-        if (*target == '\0')
+        if (target == nullptr || *target == '\0')
         {
             return ""; // 0x00 0x00 means end of the entry.
         }