diff --git a/src/ast_utils.js b/src/ast_utils.js
index 918c503..7b20b40 100644
--- a/src/ast_utils.js
+++ b/src/ast_utils.js
@@ -145,20 +145,30 @@ export const find_node = (node, pred) => {
     )
 }
 
+// TODO refactor, have explicit information if node is error origin, without
+// guessing. See also color.js
+// TODO check if return result is null and throw early
 export const find_error_origin_node = node =>
   find_node(
+    // TODO do not go inside function_expr
     node, 
     n => n.result != null && !n.result.ok && (
       n.result.error != null
       ||
-      // In case if throw null or throw undefined
-      n.type == 'throw'
-      ||
-      // await can also throw null
-      n.type == 'unary' && n.operator == 'await'
-      // or function call throwing null or undefined
-      || 
-      n.type == 'function_call'
+      // node has no error, but its children also have no error, so this node
+      // is error origin
+      n.children.find(c => find_error_origin_node(c) != null) == null
+      &&
+      (
+        // In case if throw null or throw undefined
+        n.type == 'throw'
+        ||
+        // await can also throw null
+        n.type == 'unary' && n.operator == 'await'
+        // or function call throwing null or undefined
+        || 
+        n.type == 'function_call'
+      )
     )
   )
 
diff --git a/src/color.js b/src/color.js
index aa00200..ec8e78c 100644
--- a/src/color.js
+++ b/src/color.js
@@ -13,6 +13,8 @@ const node_to_color = node => ({
       ? null
       : node.result.ok
         ? {ok: true}
+        // node.result.error may be null, for example if throw null
+        // See find_error_origin_node
         : node.result.error == null
           ? {ok: false, error_origin: false}
           : {ok: false, error_origin: true}
diff --git a/src/eval.js b/src/eval.js
index 4721c4d..76ab8c8 100644
--- a/src/eval.js
+++ b/src/eval.js
@@ -171,7 +171,7 @@ const codegen = (node, node_cxt, parent) => {
   } else if(node.type == 'object_literal'){
     const elements = 
       node.elements.map(el => {
-        if(el.type == 'spread'){
+        if(el.type == 'object_spread'){
           return do_codegen(el)
         } else if(el.type == 'identifier') {
           return el.value
@@ -241,7 +241,7 @@ const codegen = (node, node_cxt, parent) => {
       + node.operator
       + ' '
       + do_codegen(node.args[1])
-  } else if(node.type == 'spread'){
+  } else if(node.type == 'array_spread' || node.type == 'object_spread'){
     return '...(' + do_codegen(node.expr) + ')'
   } else if(node.type == 'new') {
     const args = `[${node.args.children.map(do_codegen).join(',')}]`
@@ -510,8 +510,24 @@ const do_eval_frame_expr = (node, scope, callsleft, context) => {
     // TODO exprs inside backtick string
     // Pass scope for backtick string
     return {...eval_codestring(node.value, scope), calls: callsleft}
+  } else if(node.type == 'array_spread') {
+    const result = eval_children(node, scope, callsleft, context)
+    if(!result.ok) {
+      return result
+    }
+    const child = result.children[0]
+    if((typeof(child.result.value?.[Symbol.iterator])) == 'function') {
+      return result
+    } else {
+      return {
+        ok: false,
+        children: result.children,
+        calls: result.calls,
+        error: new TypeError(child.string + ' is not iterable'),
+      }
+    }
   } else if([
-    'spread',
+    'object_spread',
     'key_value_pair',
     'computed_property'
   ].includes(node.type)) {
@@ -523,8 +539,7 @@ const do_eval_frame_expr = (node, scope, callsleft, context) => {
     }
     const value = children.reduce(
       (arr, el) => {
-        if(el.type == 'spread') {
-          // TODO check if iterable and throw error
+        if(el.type == 'array_spread') {
           return [...arr, ...el.children[0].result.value]
         } else {
           return [...arr, el.result.value]
@@ -540,7 +555,7 @@ const do_eval_frame_expr = (node, scope, callsleft, context) => {
     }
     const value = children.reduce(
       (value, el) => {
-        if(el.type == 'spread'){
+        if(el.type == 'object_spread'){
           return {...value, ...el.children[0].result.value}
         } else if(el.type == 'identifier') {
           // TODO check that it works
diff --git a/src/parse_js.js b/src/parse_js.js
index 1559d0b..426e389 100644
--- a/src/parse_js.js
+++ b/src/parse_js.js
@@ -828,7 +828,12 @@ const array_element = either(
       literal('...'),
       cxt => expr(cxt),
     ]),
-    ({value, ...node}) => ({...node, type: 'spread', not_evaluatable: true, children: [value]})
+    ({value, ...node}) => ({
+      ...node, 
+      type: 'array_spread', 
+      not_evaluatable: true, 
+      children: [value]
+    })
   ),
   cxt => expr(cxt),
 )
@@ -857,7 +862,12 @@ const object_literal =
             literal('...'),
             cxt => expr(cxt),
           ]),
-          ({value, ...node}) => ({...node, type: 'spread', children: [value], not_evaluatable: true})
+          ({value, ...node}) => ({
+            ...node, 
+            type: 'object_spread', 
+            children: [value], 
+            not_evaluatable: true
+          })
         ),
 
         // Or key-value pair
@@ -1456,7 +1466,7 @@ const update_children_not_rec = (node, children = node.children) => {
     }
   } else if(node.type == 'call_args') {
     return node
-  } else if(node.type == 'spread') {
+  } else if(node.type == 'array_spread' || node.type == 'object_spread') {
     return {...node,
       expr: children[0],
     }
diff --git a/test/test.js b/test/test.js
index 81505d8..3521cf1 100644
--- a/test/test.js
+++ b/test/test.js
@@ -837,6 +837,23 @@ export const tests = [
     )
   }),
 
+  test('array spread not iterable', () => {
+    assert_code_error(
+      `[...null]`,
+      new Error('null is not iterable'),
+    )
+  }),
+
+  test('args spread not iterable', () => {
+    assert_code_error(
+      `
+        function x() {} 
+        x(...null)
+      `,
+      new Error('null is not iterable'),
+    )
+  }),
+
   test('module not found', () => {
     const parsed = parse_modules(
       'a',
@@ -2336,6 +2353,20 @@ const y = x()`
     assert_equal(s2.value_explorer.result.error.message, 'boom')
   }),
 
+  test('move_cursor error in fn args bug', () => {
+    const code = `
+    function x() {} 
+    x(null.foo)
+    `
+    const i = test_initial_state(code)
+    
+    const m = COMMANDS.move_cursor(i, code.indexOf('x(null'))
+    assert_equal(
+      m.value_explorer.result.error, 
+      new Error("Cannot read properties of null (reading 'foo')")
+    )
+  }),
+
   test('frame follows cursor toplevel', () => {
     const code = `
       const x = () => {
diff --git a/test/utils.js b/test/utils.js
index 5881d94..61da4b5 100644
--- a/test/utils.js
+++ b/test/utils.js
@@ -1,3 +1,4 @@
+import {find_error_origin_node} from '../src/ast_utils.js'
 import {parse, print_debug_node, load_modules} from '../src/parse_js.js'
 import {eval_modules} from '../src/eval.js'
 import {active_frame, pp_calltree} from '../src/calltree.js'
@@ -81,9 +82,8 @@ export const assert_code_evals_to = (codestring, expected) => {
 export const assert_code_error = (codestring, error) => {
   const state = test_initial_state(codestring)
   const frame = active_frame(state)
-  const result = frame.children.at(-1).result
-  assert_equal(result.ok, false)
-  assert_equal(result.error, error)
+  assert_equal(frame.result.ok, false)
+  assert_equal(find_error_origin_node(frame).result.error, error)
 }
 
 export const assert_code_evals_to_async = async (codestring, expected) => {
@@ -168,9 +168,10 @@ export const test_deferred_calls_state = code => {
 
 export const stringify = val => 
   JSON.stringify(val, (key, value) => {
-    // TODO do not use instanceof because currently not implemented in parser
-    if(value?.constructor == Set){
+    if(value instanceof Set){
       return [...value]
+    } else if(value instanceof Error) {
+      return {message: value.message}
     } else {
       return value
     }