<p><b>@benpicco</b> commented on this pull request.</p>

<p>Needs a rebase now that  <a class="issue-link js-issue-link" data-error-text="Failed to load issue title" data-id="444402885" data-permission-text="Issue title is private" data-url="https://github.com/RIOT-OS/RIOT/issues/11527" data-hovercard-type="pull_request" data-hovercard-url="/RIOT-OS/RIOT/pull/11527/hovercard" href="https://github.com/RIOT-OS/RIOT/pull/11527">#11527</a> is merged.</p><hr>

<p>In <a href="https://github.com/RIOT-OS/RIOT/pull/11556#discussion_r306776789">cpu/nrf5x_common/periph/wdt.c</a>:</p>
<pre style='color:#555'>> +    DEBUG("[wdt] setting CRV to %"PRIu32"\n", crv);
+    NRF_WDT->CRV = crv;
+
+    DEBUG("[wdt] CRV configuration: %"PRIu32"\n", NRF_WDT->CRV);
+
+    /* Enable reload requests */
+    NRF_WDT->RREN = (WDT_RREN_RR0_Enabled << WDT_RREN_RR0_Pos);
+
+    DEBUG("[wdt] watchdog setup complete\n");
+}
+
+#ifdef MODULE_PERIPH_WDT_CB
+void wdt_setup_callback(uint32_t min_time, uint32_t max_time,
+                        wdt_cb_t cb, void* arg)
+{
+    wdt_cb = cb;
</pre>
<p>What if <code>cb == NULL</code>?</p>

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