diff --git a/include/wx/generic/spinctlg.h b/include/wx/generic/spinctlg.h
index 8f3e5ecc92..4c64ade837 100644
--- a/include/wx/generic/spinctlg.h
+++ b/include/wx/generic/spinctlg.h
@@ -416,7 +416,6 @@ protected:
     virtual bool DoTextToValue(const wxString& text, double *val) wxOVERRIDE;
     virtual wxString DoValueToText(double val) wxOVERRIDE;
     virtual void ResetTextValidator() wxOVERRIDE;
-    void DetermineDigits(double inc);
 
     unsigned m_digits;
 
@@ -428,6 +427,9 @@ private:
         m_format = wxASCII_STR("%0.0f");
     }
 
+    // Update m_digits and m_format to correspond to the given increment.
+    void DetermineDigits(double inc);
+
     wxString m_format;
 
     wxDECLARE_DYNAMIC_CLASS(wxSpinCtrlDouble);