diff --git a/hermit/libkern/stdio.c b/hermit/libkern/stdio.c
index 4983ce9a3..e673458ac 100644
--- a/hermit/libkern/stdio.c
+++ b/hermit/libkern/stdio.c
@@ -62,6 +62,10 @@ int kputchar(int c)
 {
 	int pos;
 
+	/* add place holder for end of string */
+	if (!c)
+		c = '?';
+
 	if (early_print != NO_EARLY_PRINT)
 		spinlock_irqsave_lock(&olock);