diff --git a/ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll b/ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll
index b24e13d74d8..1fd3ac8ec72 100644
--- a/ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll
+++ b/ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll
@@ -141,7 +141,14 @@ abstract private class StandardNode extends ControlFlowTree {
   abstract AstNode getChildNode(int i);
 
   private AstNode getChildNodeRanked(int i) {
-    result = rank[i + 1](AstNode child, int j | child = this.getChildNode(j) | child order by j)
+    result =
+      rank[i + 1](AstNode child, int j |
+        child = this.getChildNode(j) and
+        // Never descend into children with a separate scope
+        not child instanceof CfgScope
+      |
+        child order by j
+      )
   }
 
   /** Gets the first child node of this element. */
@@ -150,24 +157,17 @@ abstract private class StandardNode extends ControlFlowTree {
   /** Gets the last child node of this node. */
   final AstNode getLastChildNode() {
     exists(int last |
-      last = max(int i | exists(this.getChildNodeRanked(i))) and
-      result = this.getChildNodeRanked(last)
+      result = this.getChildNodeRanked(last) and
+      not exists(this.getChildNodeRanked(last + 1))
     )
   }
 
-  /** Gets the `i`th child, which is not the last node. */
-  pragma[nomagic]
-  private AstNode getNonLastChildNode(int i) {
-    result = this.getChildNodeRanked(i) and
-    not result = this.getLastChildNode()
-  }
-
-  final override predicate propagatesAbnormal(AstNode child) { child = this.getChildNode(_) }
+  final override predicate propagatesAbnormal(AstNode child) { child = this.getChildNodeRanked(_) }
 
   pragma[nomagic]
   override predicate succ(AstNode pred, AstNode succ, Completion c) {
     exists(int i |
-      last(this.getNonLastChildNode(i), pred, c) and
+      last(this.getChildNodeRanked(i), pred, c) and
       c instanceof NormalCompletion and
       first(this.getChildNodeRanked(i + 1), succ)
     )
@@ -428,7 +428,7 @@ private module Trees {
     final override AstNode getChildNode(int i) { result = this.getChild(i) }
   }
 
-  private class ProgramTree extends StandardPostOrderTree, Program {
+  private class ProgramTree extends StandardPreOrderTree, Program {
     final override AstNode getChildNode(int i) { result = this.getChild(i) }
 
     override predicate isHidden() { any() }
diff --git a/ql/test/library-tests/controlflow/graph/Cfg.expected b/ql/test/library-tests/controlflow/graph/Cfg.expected
index 8ced58f5173..5bb2e3b2a6f 100644
--- a/ql/test/library-tests/controlflow/graph/Cfg.expected
+++ b/ql/test/library-tests/controlflow/graph/Cfg.expected
@@ -3,9 +3,6 @@ nodes
 | exit.rb:1:1:6:3 | exit m1 |
 | exit.rb:1:1:6:3 | exit m1 (abnormal) |
 | exit.rb:1:1:6:3 | exit m1 (normal) |
-| exit.rb:1:1:13:4 | enter top-level |
-| exit.rb:1:1:13:4 | exit top-level |
-| exit.rb:1:1:13:4 | exit top-level (abnormal) |
 | exit.rb:2:3:4:5 | If |
 | exit.rb:2:6:2:6 | x |
 | exit.rb:2:6:2:10 | Binary |
@@ -33,9 +30,6 @@ nodes
 | ifs.rb:1:1:9:3 | enter m1 |
 | ifs.rb:1:1:9:3 | exit m1 |
 | ifs.rb:1:1:9:3 | exit m1 (normal) |
-| ifs.rb:1:1:26:4 | enter top-level |
-| ifs.rb:1:1:26:4 | exit top-level |
-| ifs.rb:1:1:26:4 | exit top-level (normal) |
 | ifs.rb:2:3:8:5 | If |
 | ifs.rb:2:6:2:6 | x |
 | ifs.rb:2:6:2:10 | Binary |
@@ -102,7 +96,6 @@ nodes
 | loops.rb:1:1:6:3 | enter m1 |
 | loops.rb:1:1:6:3 | exit m1 |
 | loops.rb:1:1:6:3 | exit m1 (normal) |
-| loops.rb:1:1:28:3 | enter top-level |
 | loops.rb:2:3:5:5 | While |
 | loops.rb:2:9:2:9 | x |
 | loops.rb:2:9:2:14 | Binary |
@@ -167,9 +160,6 @@ nodes
 | raise.rb:1:1:6:3 | exit m1 |
 | raise.rb:1:1:6:3 | exit m1 (abnormal) |
 | raise.rb:1:1:6:3 | exit m1 (normal) |
-| raise.rb:1:1:6:4 | enter top-level |
-| raise.rb:1:1:6:4 | exit top-level |
-| raise.rb:1:1:6:4 | exit top-level (abnormal) |
 | raise.rb:2:3:4:5 | If |
 | raise.rb:2:6:2:6 | x |
 | raise.rb:2:6:2:10 | Binary |
@@ -184,8 +174,6 @@ edges
 | exit.rb:1:1:6:3 | enter m1 | exit.rb:2:3:4:5 | If | semmle.label | successor |
 | exit.rb:1:1:6:3 | exit m1 (abnormal) | exit.rb:1:1:6:3 | exit m1 | semmle.label | successor |
 | exit.rb:1:1:6:3 | exit m1 (normal) | exit.rb:1:1:6:3 | exit m1 | semmle.label | successor |
-| exit.rb:1:1:13:4 | enter top-level | exit.rb:2:3:4:5 | If | semmle.label | successor |
-| exit.rb:1:1:13:4 | exit top-level (abnormal) | exit.rb:1:1:13:4 | exit top-level | semmle.label | successor |
 | exit.rb:2:3:4:5 | If | exit.rb:2:6:2:6 | x | semmle.label | successor |
 | exit.rb:2:6:2:6 | x | exit.rb:2:10:2:10 | 2 | semmle.label | successor |
 | exit.rb:2:6:2:10 | Binary | exit.rb:3:10:3:10 | 1 | semmle.label | true |
@@ -193,11 +181,9 @@ edges
 | exit.rb:2:10:2:10 | 2 | exit.rb:2:6:2:10 | Binary | semmle.label | successor |
 | exit.rb:3:5:3:8 | exit | exit.rb:3:5:3:10 | MethodCall | semmle.label | successor |
 | exit.rb:3:5:3:10 | MethodCall | exit.rb:1:1:6:3 | exit m1 (abnormal) | semmle.label | exit |
-| exit.rb:3:5:3:10 | MethodCall | exit.rb:1:1:13:4 | exit top-level (abnormal) | semmle.label | exit |
 | exit.rb:3:10:3:10 | 1 | exit.rb:3:5:3:8 | exit | semmle.label | successor |
 | exit.rb:5:3:5:6 | puts | exit.rb:5:3:5:15 | MethodCall | semmle.label | successor |
 | exit.rb:5:3:5:15 | MethodCall | exit.rb:1:1:6:3 | exit m1 (normal) | semmle.label | successor |
-| exit.rb:5:3:5:15 | MethodCall | exit.rb:9:3:11:5 | If | semmle.label | successor |
 | exit.rb:5:8:5:15 | String | exit.rb:5:3:5:6 | puts | semmle.label | successor |
 | exit.rb:8:1:13:3 | enter m2 | exit.rb:9:3:11:5 | If | semmle.label | successor |
 | exit.rb:8:1:13:3 | exit m2 (abnormal) | exit.rb:8:1:13:3 | exit m2 | semmle.label | successor |
@@ -208,7 +194,6 @@ edges
 | exit.rb:9:6:9:10 | Binary | exit.rb:12:8:12:15 | String | semmle.label | false |
 | exit.rb:9:10:9:10 | 2 | exit.rb:9:6:9:10 | Binary | semmle.label | successor |
 | exit.rb:10:5:10:9 | abort | exit.rb:10:5:10:18 | MethodCall | semmle.label | successor |
-| exit.rb:10:5:10:18 | MethodCall | exit.rb:1:1:13:4 | exit top-level (abnormal) | semmle.label | exit |
 | exit.rb:10:5:10:18 | MethodCall | exit.rb:8:1:13:3 | exit m2 (abnormal) | semmle.label | exit |
 | exit.rb:10:11:10:18 | String | exit.rb:10:5:10:9 | abort | semmle.label | successor |
 | exit.rb:12:3:12:6 | puts | exit.rb:12:3:12:15 | MethodCall | semmle.label | successor |
@@ -216,8 +201,6 @@ edges
 | exit.rb:12:8:12:15 | String | exit.rb:12:3:12:6 | puts | semmle.label | successor |
 | ifs.rb:1:1:9:3 | enter m1 | ifs.rb:2:3:8:5 | If | semmle.label | successor |
 | ifs.rb:1:1:9:3 | exit m1 (normal) | ifs.rb:1:1:9:3 | exit m1 | semmle.label | successor |
-| ifs.rb:1:1:26:4 | enter top-level | ifs.rb:2:3:8:5 | If | semmle.label | successor |
-| ifs.rb:1:1:26:4 | exit top-level (normal) | ifs.rb:1:1:26:4 | exit top-level | semmle.label | successor |
 | ifs.rb:2:3:8:5 | If | ifs.rb:2:6:2:6 | x | semmle.label | successor |
 | ifs.rb:2:6:2:6 | x | ifs.rb:2:10:2:10 | 2 | semmle.label | successor |
 | ifs.rb:2:6:2:10 | Binary | ifs.rb:3:10:3:30 | String | semmle.label | true |
@@ -225,7 +208,6 @@ edges
 | ifs.rb:2:10:2:10 | 2 | ifs.rb:2:6:2:10 | Binary | semmle.label | successor |
 | ifs.rb:3:5:3:8 | puts | ifs.rb:3:5:3:30 | MethodCall | semmle.label | successor |
 | ifs.rb:3:5:3:30 | MethodCall | ifs.rb:1:1:9:3 | exit m1 (normal) | semmle.label | successor |
-| ifs.rb:3:5:3:30 | MethodCall | ifs.rb:12:3:14:5 | If | semmle.label | successor |
 | ifs.rb:3:10:3:30 | String | ifs.rb:3:5:3:8 | puts | semmle.label | successor |
 | ifs.rb:4:3:7:35 | Elsif | ifs.rb:4:9:4:9 | x | semmle.label | successor |
 | ifs.rb:4:9:4:9 | x | ifs.rb:4:14:4:14 | 2 | semmle.label | successor |
@@ -250,21 +232,17 @@ edges
 | ifs.rb:4:37:4:37 | 5 | ifs.rb:4:32:4:37 | Binary | semmle.label | successor |
 | ifs.rb:5:5:5:8 | puts | ifs.rb:5:5:5:17 | MethodCall | semmle.label | successor |
 | ifs.rb:5:5:5:17 | MethodCall | ifs.rb:1:1:9:3 | exit m1 (normal) | semmle.label | successor |
-| ifs.rb:5:5:5:17 | MethodCall | ifs.rb:12:3:14:5 | If | semmle.label | successor |
 | ifs.rb:5:10:5:17 | String | ifs.rb:5:5:5:8 | puts | semmle.label | successor |
 | ifs.rb:7:5:7:8 | puts | ifs.rb:7:5:7:35 | MethodCall | semmle.label | successor |
 | ifs.rb:7:5:7:35 | MethodCall | ifs.rb:1:1:9:3 | exit m1 (normal) | semmle.label | successor |
-| ifs.rb:7:5:7:35 | MethodCall | ifs.rb:12:3:14:5 | If | semmle.label | successor |
 | ifs.rb:7:10:7:35 | String | ifs.rb:7:5:7:8 | puts | semmle.label | successor |
 | ifs.rb:11:1:16:3 | enter m2 | ifs.rb:12:3:14:5 | If | semmle.label | successor |
 | ifs.rb:11:1:16:3 | exit m2 (normal) | ifs.rb:11:1:16:3 | exit m2 | semmle.label | successor |
 | ifs.rb:12:3:14:5 | If | ifs.rb:12:6:12:6 | b | semmle.label | successor |
 | ifs.rb:12:6:12:6 | b | ifs.rb:13:12:13:12 | 0 | semmle.label | true |
 | ifs.rb:12:6:12:6 | b | ifs.rb:15:10:15:10 | 1 | semmle.label | false |
-| ifs.rb:13:5:13:12 | Return | ifs.rb:1:1:26:4 | exit top-level (normal) | semmle.label | return |
 | ifs.rb:13:5:13:12 | Return | ifs.rb:11:1:16:3 | exit m2 (normal) | semmle.label | return |
 | ifs.rb:13:12:13:12 | 0 | ifs.rb:13:5:13:12 | Return | semmle.label | successor |
-| ifs.rb:15:3:15:10 | Return | ifs.rb:1:1:26:4 | exit top-level (normal) | semmle.label | return |
 | ifs.rb:15:3:15:10 | Return | ifs.rb:11:1:16:3 | exit m2 (normal) | semmle.label | return |
 | ifs.rb:15:10:15:10 | 1 | ifs.rb:15:3:15:10 | Return | semmle.label | successor |
 | ifs.rb:18:1:26:3 | enter m3 | ifs.rb:19:3:24:5 | If | semmle.label | successor |
@@ -293,12 +271,10 @@ edges
 | ifs.rb:25:8:25:8 | x | ifs.rb:25:3:25:6 | puts | semmle.label | successor |
 | loops.rb:1:1:6:3 | enter m1 | loops.rb:2:3:5:5 | While | semmle.label | successor |
 | loops.rb:1:1:6:3 | exit m1 (normal) | loops.rb:1:1:6:3 | exit m1 | semmle.label | successor |
-| loops.rb:1:1:28:3 | enter top-level | loops.rb:2:3:5:5 | While | semmle.label | successor |
 | loops.rb:2:3:5:5 | While | loops.rb:2:9:2:9 | x | semmle.label | successor |
 | loops.rb:2:9:2:9 | x | loops.rb:2:14:2:14 | 0 | semmle.label | successor |
 | loops.rb:2:9:2:14 | Binary | loops.rb:1:1:6:3 | exit m1 (normal) | semmle.label | false |
 | loops.rb:2:9:2:14 | Binary | loops.rb:3:10:3:10 | x | semmle.label | true |
-| loops.rb:2:9:2:14 | Binary | loops.rb:9:3:20:5 | While | semmle.label | false |
 | loops.rb:2:14:2:14 | 0 | loops.rb:2:9:2:14 | Binary | semmle.label | successor |
 | loops.rb:3:5:3:8 | puts | loops.rb:3:5:3:10 | MethodCall | semmle.label | successor |
 | loops.rb:3:5:3:10 | MethodCall | loops.rb:4:5:4:5 | x | semmle.label | successor |
@@ -342,7 +318,6 @@ edges
 | loops.rb:19:10:19:15 | String | loops.rb:19:5:19:8 | puts | semmle.label | successor |
 | loops.rb:21:3:21:6 | puts | loops.rb:21:3:21:13 | MethodCall | semmle.label | successor |
 | loops.rb:21:3:21:13 | MethodCall | loops.rb:8:1:22:3 | exit m2 (normal) | semmle.label | successor |
-| loops.rb:21:3:21:13 | MethodCall | loops.rb:25:4:25:4 | 1 | semmle.label | successor |
 | loops.rb:21:8:21:13 | String | loops.rb:21:3:21:6 | puts | semmle.label | successor |
 | loops.rb:24:1:28:3 | enter m3 | loops.rb:25:4:25:4 | 1 | semmle.label | successor |
 | loops.rb:24:1:28:3 | exit m3 (normal) | loops.rb:24:1:28:3 | exit m3 | semmle.label | successor |
@@ -361,8 +336,6 @@ edges
 | raise.rb:1:1:6:3 | enter m1 | raise.rb:2:3:4:5 | If | semmle.label | successor |
 | raise.rb:1:1:6:3 | exit m1 (abnormal) | raise.rb:1:1:6:3 | exit m1 | semmle.label | successor |
 | raise.rb:1:1:6:3 | exit m1 (normal) | raise.rb:1:1:6:3 | exit m1 | semmle.label | successor |
-| raise.rb:1:1:6:4 | enter top-level | raise.rb:2:3:4:5 | If | semmle.label | successor |
-| raise.rb:1:1:6:4 | exit top-level (abnormal) | raise.rb:1:1:6:4 | exit top-level | semmle.label | successor |
 | raise.rb:2:3:4:5 | If | raise.rb:2:6:2:6 | x | semmle.label | successor |
 | raise.rb:2:6:2:6 | x | raise.rb:2:10:2:10 | 2 | semmle.label | successor |
 | raise.rb:2:6:2:10 | Binary | raise.rb:3:11:3:17 | String | semmle.label | true |
@@ -370,7 +343,6 @@ edges
 | raise.rb:2:10:2:10 | 2 | raise.rb:2:6:2:10 | Binary | semmle.label | successor |
 | raise.rb:3:5:3:9 | raise | raise.rb:3:5:3:17 | MethodCall | semmle.label | successor |
 | raise.rb:3:5:3:17 | MethodCall | raise.rb:1:1:6:3 | exit m1 (abnormal) | semmle.label | raise |
-| raise.rb:3:5:3:17 | MethodCall | raise.rb:1:1:6:4 | exit top-level (abnormal) | semmle.label | raise |
 | raise.rb:3:11:3:17 | String | raise.rb:3:5:3:9 | raise | semmle.label | successor |
 | raise.rb:5:3:5:6 | puts | raise.rb:5:3:5:15 | MethodCall | semmle.label | successor |
 | raise.rb:5:3:5:15 | MethodCall | raise.rb:1:1:6:3 | exit m1 (normal) | semmle.label | successor |