diff --git a/src/Catena_Download.h b/src/Catena_Download.h
index b7d49d5..e393657 100644
--- a/src/Catena_Download.h
+++ b/src/Catena_Download.h
@@ -24,6 +24,8 @@ Copyright and License:
 #ifndef _catena_download_h_
 #define _catena_download_h_
 
+#ifdef ARDUINO_STM32
+
 #include <cstdarg>
 #include <Catena_BootloaderApi.h>
 #include <Catena_Flash.h>
@@ -284,4 +286,6 @@ class cDownload : public cPollableObject
 
 } // McciCatena
 
+#endif // ARDUINO_STM32
+
 #endif // _catena_download_h_
diff --git a/src/lib/Catena_Download.cpp b/src/lib/Catena_Download.cpp
index 347719a..ecfc3ce 100644
--- a/src/lib/Catena_Download.cpp
+++ b/src/lib/Catena_Download.cpp
@@ -21,6 +21,8 @@ Copyright and License:
 
 #include "Catena_Download.h"
 
+#ifdef ARDUINO_STM32
+
 #include <Catena_BootloaderApi.h>
 #include <Catena_Flash.h>
 #include <Catena_Log.h>
@@ -590,3 +592,5 @@ cDownload::evStartSerialDownload(
     // launch the request.
     return evStart(request);
     }
+
+#endif ARDUINO_STM32