diff --git a/tensorflow/lite/micro/stm32f4HAL/debug_log.cc b/tensorflow/lite/micro/stm32f4HAL/debug_log.cc
index 9a70998d9d5..4be3b40e782 100644
--- a/tensorflow/lite/micro/stm32f4HAL/debug_log.cc
+++ b/tensorflow/lite/micro/stm32f4HAL/debug_log.cc
@@ -20,18 +20,20 @@ limitations under the License.
 
 #include <cstdio>
 
-#ifdef __GNUC__
-#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
-#else
-#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
-#endif /* __GNUC__ */
-
 extern UART_HandleTypeDef DEBUG_UART_HANDLE;
 
-PUTCHAR_PROTOTYPE {
+#ifdef __GNUC__
+int __io_putchar(int ch) {
   HAL_UART_Transmit(&DEBUG_UART_HANDLE, (uint8_t *)&ch, 1, HAL_MAX_DELAY);
 
   return ch;
 }
+#else
+int fputc(int ch, FILE *f) {
+  HAL_UART_Transmit(&DEBUG_UART_HANDLE, (uint8_t *)&ch, 1, HAL_MAX_DELAY);
+
+  return ch;
+}
+#endif /* __GNUC__ */
 
 extern "C" void DebugLog(const char *s) { fprintf(stderr, "%s", s); }