diff --git a/apps/app_milliwatt.c b/apps/app_milliwatt.c
index 4214141261..75d8037d61 100644
--- a/apps/app_milliwatt.c
+++ b/apps/app_milliwatt.c
@@ -78,7 +78,7 @@ static void milliwatt_release(struct ast_channel *chan, void *data)
 static int milliwatt_generate(struct ast_channel *chan, void *data, int len, int samples)
 {
 	unsigned char buf[AST_FRIENDLY_OFFSET + 640];
-	const int maxsamples = ARRAY_LEN(buf);
+	const int maxsamples = ARRAY_LEN(buf) - (AST_FRIENDLY_OFFSET / sizeof(buf[0]));
 	int i, *indexp = (int *) data;
 	struct ast_frame wf = {
 		.frametype = AST_FRAME_VOICE,