diff --git a/windows/dialog.c b/windows/dialog.c
index 747b5336..f65c8a61 100644
--- a/windows/dialog.c
+++ b/windows/dialog.c
@@ -621,11 +621,13 @@ static INT_PTR GenericMainDlgProc(HWND hwnd, UINT msg, WPARAM wParam,
         if (dialog_box_demo_screenshot_filename &&
             (UINT_PTR)wParam == DEMO_SCREENSHOT_TIMER_ID) {
             KillTimer(hwnd, DEMO_SCREENSHOT_TIMER_ID);
-            const char *err = save_screenshot(
+            char *err = save_screenshot(
                 hwnd, dialog_box_demo_screenshot_filename);
-            if (err)
+            if (err) {
                 MessageBox(hwnd, err, "Demo screenshot failure",
                            MB_OK | MB_ICONERROR);
+                sfree(err);
+            }
             ShinyEndDialog(hwnd, 0);
         }
         return 0;
diff --git a/windows/putty.c b/windows/putty.c
index 53c8b4a5..823d0a30 100644
--- a/windows/putty.c
+++ b/windows/putty.c
@@ -180,7 +180,11 @@ const wchar_t *get_app_user_model_id(void)
 static void demo_terminal_screenshot(void *ctx, unsigned long now)
 {
     HWND hwnd = (HWND)ctx;
-    save_screenshot(hwnd, terminal_demo_screenshot_filename);
+    char *err = save_screenshot(hwnd, terminal_demo_screenshot_filename);
+    if (err) {
+        MessageBox(hwnd, err, "Demo screenshot failure", MB_OK | MB_ICONERROR);
+        sfree(err);
+    }
     cleanup_exit(0);
 }
 
diff --git a/windows/puttygen.c b/windows/puttygen.c
index 5beaed12..ea3557b0 100644
--- a/windows/puttygen.c
+++ b/windows/puttygen.c
@@ -1592,10 +1592,12 @@ static INT_PTR CALLBACK MainDlgProc(HWND hwnd, UINT msg,
       case WM_TIMER:
         if ((UINT_PTR)wParam == DEMO_SCREENSHOT_TIMER_ID) {
             KillTimer(hwnd, DEMO_SCREENSHOT_TIMER_ID);
-            const char *err = save_screenshot(hwnd, demo_screenshot_filename);
-            if (err)
+            char *err = save_screenshot(hwnd, demo_screenshot_filename);
+            if (err) {
                 MessageBox(hwnd, err, "Demo screenshot failure",
                            MB_OK | MB_ICONERROR);
+                sfree(err);
+            }
             EndDialog(hwnd, 0);
         }
         return 0;