diff --git a/hardware1.hpp b/hardware1.hpp
index 22e4c15..05d9494 100644
--- a/hardware1.hpp
+++ b/hardware1.hpp
@@ -127,10 +127,14 @@ class Hardware1<cfg, Driven::INTERRUPT, mode>
 	}
 };
 
+#endif
+
 } // namespace uart
 
 //////////////////////////////////////////////////////////////////////////
 
+#ifdef HAS_UART1
+
 // Forward declare interrupt functions to allow adding them as friends
 extern "C" {
 void USART1_RX_vect() __attribute__((signal));