diff --git a/src/slic3r/GUI/Tab.cpp b/src/slic3r/GUI/Tab.cpp
index 32131d99d..bc4c6b728 100644
--- a/src/slic3r/GUI/Tab.cpp
+++ b/src/slic3r/GUI/Tab.cpp
@@ -1747,14 +1747,14 @@ bool Tab::validate_custom_gcode(const wxString& title, const std::string& gcode)
     std::vector<std::string> tags;
     bool invalid = GCodeProcessor::contains_reserved_tags(gcode, 5, tags);
     if (invalid) {
-        wxString reports = _L_PLURAL("The following line", "The following lines", tags.size());
-        reports += ":\n";
-        for (const std::string& keyword : tags) {
-            reports += ";" + keyword + "\n";
-        }
-        reports += _L("contain reserved keywords.") + "\n";
-        reports += _L("Please remove them, as they may cause problems in g-code visualization and printing time estimation.");
-
+        std::string lines = ":\n";
+        for (const std::string& keyword : tags)
+            lines += ";" + keyword + "\n";
+        wxString reports = format_wxstr(
+            _L_PLURAL("The following line %s contains reserved keywords.\nPlease remove it, as it may cause problems in G-code visualization and printing time estimation.", 
+                      "The following lines %s contain reserved keywords.\nPlease remove them, as they may cause problems in G-code visualization and printing time estimation.", 
+                      tags.size()),
+            lines);
         //wxMessageDialog dialog(wxGetApp().mainframe, reports, _L("Found reserved keywords in") + " " + _(title), wxICON_WARNING | wxOK);
         MessageDialog dialog(wxGetApp().mainframe, reports, _L("Found reserved keywords in") + " " + _(title), wxICON_WARNING | wxOK);
         dialog.ShowModal();