diff --git a/src/script.c b/src/script.c
index f6023eb..b471932 100644
--- a/src/script.c
+++ b/src/script.c
@@ -207,6 +207,11 @@ static int write_(lua_State *L)
 // Function to add a character to the circular expect buffer
 static void expect_buffer_add(char c)
 {
+    if (!c)
+    {
+        return;
+    }
+
     if (buffer_size < MAX_BUFFER_SIZE)
     {
         circular_buffer[buffer_size++] = c;