diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index ff00768807..f2deba0467 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -2642,9 +2642,23 @@ std::string GCode::extrude_support(const ExtrusionEntityCollection &support_fill
     return gcode;
 }
 
-bool GCode::GCodeOutputStream::is_error() const { return ::ferror(f); }
-void GCode::GCodeOutputStream::flush() { ::fflush(f); }
-void GCode::GCodeOutputStream::close() { if (f) ::fclose(f); }
+bool GCode::GCodeOutputStream::is_error() const 
+{
+    return ::ferror(this->f);
+}
+
+void GCode::GCodeOutputStream::flush()
+{ 
+    ::fflush(this->f);
+}
+
+void GCode::GCodeOutputStream::close()
+{ 
+    if (this->f) {
+        ::fclose(this->f);
+        this->f = nullptr;
+    }
+}
 
 void GCode::GCodeOutputStream::write(const char *what)
 {
diff --git a/src/libslic3r/GCode/GCodeProcessor.cpp b/src/libslic3r/GCode/GCodeProcessor.cpp
index ec586dbef7..60af399c06 100644
--- a/src/libslic3r/GCode/GCodeProcessor.cpp
+++ b/src/libslic3r/GCode/GCodeProcessor.cpp
@@ -350,7 +350,12 @@ void GCodeProcessor::TimeProcessor::reset()
 struct FilePtr {
     FilePtr(FILE *f) : f(f) {}
     ~FilePtr() { this->close(); }
-    void close() { if (f) ::fclose(f); }
+    void close() { 
+        if (this->f) {
+            ::fclose(this->f);
+            this->f = nullptr;
+        }
+    }
     FILE* f = nullptr;
 };