diff --git a/dll/cpl/openglcfg/general.c b/dll/cpl/openglcfg/general.c
index f9376ed0b8c..69170a4232f 100644
--- a/dll/cpl/openglcfg/general.c
+++ b/dll/cpl/openglcfg/general.c
@@ -190,13 +190,14 @@ INT_PTR CALLBACK GeneralPageProc(HWND hWndDlg, UINT uMsg, WPARAM wParam, LPARAM
             break;
 
         case WM_DESTROY:
-             {
+            if (pOglDrivers != NULL)
+            {
                 INT iKey;
                 for (iKey = 0; iKey <= dwNumDrivers; iKey++)
                     HeapFree(GetProcessHeap(), 0, pOglDrivers[iKey]);
 
                 HeapFree(GetProcessHeap(), 0, pOglDrivers);
-             }
+            }
     }
 
     return FALSE;