diff --git a/lib/os/printk.c b/lib/os/printk.c
index c7c276503e2..29d62b7749d 100644
--- a/lib/os/printk.c
+++ b/lib/os/printk.c
@@ -210,8 +210,9 @@ struct str_context {
 	int count;
 };
 
-static int str_out(int c, struct str_context *ctx)
+static int str_out(int c, void *context)
 {
+	struct str_context *ctx = context;
 	if ((ctx->str == NULL) || (ctx->count >= ctx->max)) {
 		++ctx->count;
 		return c;