diff --git a/cores/arduino/pinDefinitions.h b/cores/arduino/pinDefinitions.h
index 4ba117f34..7df17a804 100644
--- a/cores/arduino/pinDefinitions.h
+++ b/cores/arduino/pinDefinitions.h
@@ -29,9 +29,7 @@ struct _AnalogPinDescription
 #ifdef __cplusplus__
 extern "C" {
 #endif
-inline PinName digitalPinToPinName(pin_size_t P) {
-	return (P >= PINS_COUNT ? NC : g_APinDescription[P].name);
-};
+PinName digitalPinToPinName(pin_size_t P);
 #ifdef __cplusplus__
 }
 #endif
diff --git a/cores/arduino/pinToIndex.cpp b/cores/arduino/pinToIndex.cpp
index 094557033..01817e97d 100644
--- a/cores/arduino/pinToIndex.cpp
+++ b/cores/arduino/pinToIndex.cpp
@@ -9,3 +9,13 @@ int PinNameToIndex(PinName P) {
   }
   return NOT_A_PIN;
 }
+
+#ifdef __cplusplus__
+extern "C" {
+#endif
+PinName digitalPinToPinName(pin_size_t P) {
+  return (P >= PINS_COUNT ? NC : g_APinDescription[P].name);
+};
+#ifdef __cplusplus__
+}
+#endif
\ No newline at end of file