diff --git a/packages/ludic.ui/backend.ludic b/packages/ludic.ui/backend.ludic
index 584d735e..9d59d10c 100644
--- a/packages/ludic.ui/backend.ludic
+++ b/packages/ludic.ui/backend.ludic
@@ -43,7 +43,7 @@ export state UiState {
   mm_ivals: []Val = null
   ev_depth: int = 0                      # eval.ludic: a call's arguments, in lists kept one a depth
   ev_args: []Val = new []Val
-  @max(64) ev_ring: []Val = new []Val             # eval.ludic: calls' answers while an action runs, EV_RING of them
+  @max(64) ev_ring: []Val = ev_ring_new()         # eval.ludic: calls' answers while an action runs, EV_RING of them, made with the state
   ev_ring_at: int = 0
   cv_texts: []string = new []string      # units_pieces.ludic: a value's var() pieces, kept
   tx_pieces: [][]string = new [][]string # eval_text.ludic: a text's pieces, a list a depth
diff --git a/packages/ludic.ui/controls_build.ludic b/packages/ludic.ui/controls_build.ludic
index 0ebb8779..18f6122d 100644
--- a/packages/ludic.ui/controls_build.ludic
+++ b/packages/ludic.ui/controls_build.ludic
@@ -20,11 +20,11 @@ function ct_part(ui_st: mut UiState, n: UiNode, cls: string, text: string) -> Ui
 # <progress value max> and <meter value min max>: a track with a fill as far as the value
 function ct_build_bar(ui_st: mut UiState, n: UiNode) -> void {
   n.dir = UI_ROW
-  let lo = Value.as_float(ui_attr(n, "min"))
-  var hi = Value.as_float(ui_attr(n, "max"))
+  let lo = ui_attr_float(n, "min", 0.0)
+  var hi = ui_attr_float(n, "max", 0.0)
   if hi <= lo { hi = lo + 1.0 }
   let fill = ct_part(ui_st, n, "ui-fill", "")
-  fill.w_pct = Math.clamp((Value.as_float(ui_attr(n, "value")) - lo) / (hi - lo), 0.0, 1.0) * 100.0
+  fill.w_pct = Math.clamp((ui_attr_float(n, "value", 0.0) - lo) / (hi - lo), 0.0, 1.0) * 100.0
   ui_kept(n.children, fill)
 }
 function ct_build(ui_st: mut UiState, n: UiNode) -> void {
@@ -54,10 +54,10 @@ function ct_build(ui_st: mut UiState, n: UiNode) -> void {
   }
 }
 function ct_build_range(ui_st: mut UiState, n: UiNode) -> void {
-  let lo = Value.as_float(ui_attr(n, "min"))
-  var hi = Value.as_float(ui_attr(n, "max"))
+  let lo = ui_attr_float(n, "min", 0.0)
+  var hi = ui_attr_float(n, "max", 0.0)
   if hi <= lo { hi = lo + 1.0 }
-  let v = Value.as_float(ui_attr(n, "value"))
+  let v = ui_attr_float(n, "value", 0.0)
   let track = ct_part(ui_st, n, "ui-track", "")
   let fill = ct_part(ui_st, n, "ui-fill", "")
   fill.w_pct = Math.clamp((v - lo) / (hi - lo), 0.0, 1.0) * 100.0
diff --git a/packages/ludic.ui/eval.ludic b/packages/ludic.ui/eval.ludic
index c30df4d4..49e1499c 100644
--- a/packages/ludic.ui/eval.ludic
+++ b/packages/ludic.ui/eval.ludic
@@ -77,5 +77,10 @@ function ev_into(ui_st: mut UiState) -> Val {
   return ring[at]
 }
 const EV_RING: int = 64
+function ev_ring_new() -> []Val {
+  let l = new []Val
+  for i in 0 .. EV_RING { push(l, Value.null()) }
+  return l
+}
 function ui_eval_text(ui_st: mut UiState, x: UiExpr, e: UiEnv) -> string { return vl_text(ui_eval(ui_st, x, e)) }
 function ui_eval_bool(ui_st: mut UiState, x: UiExpr, e: UiEnv) -> bool { return vl_truthy(ui_eval(ui_st, x, e)) }
diff --git a/packages/ludic.ui/native.ludic b/packages/ludic.ui/native.ludic
index f4a69575..0a040561 100644
--- a/packages/ludic.ui/native.ludic
+++ b/packages/ludic.ui/native.ludic
@@ -94,6 +94,11 @@ export function ui_attr_has(n: UiNode, key: string) -> bool {
   }
   return false
 }
+# an attribute as a number, `none` when it is not there - without ui_attr's new null for a miss
+export function ui_attr_float(n: UiNode, key: string, none: float) -> float {
+  if not ui_attr_has(n, key) { return none }
+  return Value.as_float(ui_attr(n, key))
+}
 export function ui_attr_text(n: UiNode, key: string) -> string {
   if n.akeys == null { return "" }
   for i in 0 .. len(n.akeys) {