diff --git a/Test/A05execution.ztst b/Test/A05execution.ztst
index 0804691..35efbc0 100644
--- a/Test/A05execution.ztst
+++ b/Test/A05execution.ztst
@@ -310,3 +310,17 @@ F:anonymous function, and a descriptor leak when backgrounding a pipeline
 >17
 >19
 
+# Regression test for workers/40645
+  # Bug only occurs with POSIXBUILTINS active.
+  setopt POSIXBUILTINS
+  # A dot script is needed to trigger the bug.
+  printf '%s' '
+    # Execution counter.
+    count=0
+    # Exiting from a subshell due to an error triggers the bug.
+    (set -o nonexistent_@_option) 2>/dev/null
+    # With the bug, this will be executed twice so "let" returns true (0).
+    let "(count += 1) > 1"
+  ' > 40645.t
+  . ./40645.t
+1:program flow corruption with POSIXBUILTINS after subshell error exit