diff --git a/src/nvim/tui/input.c b/src/nvim/tui/input.c
index 7af28561c2..c55cb44560 100644
--- a/src/nvim/tui/input.c
+++ b/src/nvim/tui/input.c
@@ -297,10 +297,10 @@ static void forward_simple_utf8(TermInput *input, TermKeyKey *key)
     } else {
       buf[len++] = *ptr;
     }
+    assert(len < sizeof(buf));
     ptr++;
   }
 
-  assert(len < sizeof(buf));
   tinput_enqueue(input, buf, len);
 }