diff --git a/openwsn/main.c b/openwsn/main.c
index 31cac065e5..5dec79f8ed 100644
--- a/openwsn/main.c
+++ b/openwsn/main.c
@@ -40,9 +40,11 @@ static int shell_readc(void)
     return c;
 }
 
-static void shell_putchar(int c)
+static int shell_putchar(int c)
 {
     (void) putchar(c);
+
+    return c;
 }
 
 int main(void) {
@@ -57,4 +59,4 @@ int main(void) {
     shell_run(&shell);
 
     return 0;
-}
\ No newline at end of file
+}