diff --git a/test/mocks/Arduino.h b/test/mocks/Arduino.h
index 77499fe41..a3d5b2765 100644
--- a/test/mocks/Arduino.h
+++ b/test/mocks/Arduino.h
@@ -2,8 +2,15 @@
 
 #include <cstdint>
 #include <cmath>
+// The real Arduino.h pulls in stdlib.h, so device code reaches atoi/atol/atof/strtoul
+// without including it. Mirror that here or those sources fail only on the native build.
+#include <cstdlib>
 #include "Stream.h"
 
+using std::atof;
+using std::atoi;
+using std::atol;
+
 inline uint32_t g_mock_millis = 0;
 
 using std::isnan;