diff --git a/src/libslic3r/Format/STEP.cpp b/src/libslic3r/Format/STEP.cpp
index 283fe63798..a637cdd3ca 100644
--- a/src/libslic3r/Format/STEP.cpp
+++ b/src/libslic3r/Format/STEP.cpp
@@ -182,7 +182,7 @@ static void getNamedSolids(const TopLoc_Location& location, const std::string& p
     if (referredLabel.FindAttribute(TDataStd_Name::GetID(), shapeName))
         name = TCollection_AsciiString(shapeName->Get()).ToCString();
 
-    if (name == "")
+    if (name == "" || !StepPreProcessor::isUtf8(name))
         name = std::to_string(id++);
     std::string fullName{name};
 
diff --git a/src/libslic3r/Format/STEP.hpp b/src/libslic3r/Format/STEP.hpp
index 72f8327106..64e52aa9be 100644
--- a/src/libslic3r/Format/STEP.hpp
+++ b/src/libslic3r/Format/STEP.hpp
@@ -42,8 +42,8 @@ class StepPreProcessor {
 public:
     bool preprocess(const char* path, std::string &output_path);
     static bool isUtf8File(const char* path);
-private:
     static bool isUtf8(const std::string str);
+private: 
     static bool isGBK(const std::string str);
     static int preNum(const unsigned char byte);
     //BBS: default is UTF8 for most step file.