diff --git a/igneum-pow/src/generator.rs b/igneum-pow/src/generator.rs
index f6db262c7..13ac517a5 100644
--- a/igneum-pow/src/generator.rs
+++ b/igneum-pow/src/generator.rs
@@ -1242,7 +1242,12 @@ pub fn candidate_from_words_class(
     // by `or`, `mul` or `mulhi` (an `or`-written source is all-ones with probability (3/4)^32 per read and made the
     // 153x item of the finding). Keyed on the era-composed V4_CLASS so the generator-2 ladder packs keep their stream;
     // v2 and v3 take no part. The draw order and the stream are otherwise the same, draw for draw.
-    let source_rule_v4 = ProgramClass::of_load_class(&class) == Some(ProgramClass::V4) && class.era.is_some();
+    // Keyed on the class with the shadow's pass count set aside (the latency ladder draws the same base program at
+    // every rung: `of_load_class` compares the pass count too and answered None at every rung but 27, found by the
+    // fork's ladder test, 7 October 2026 10:06Z), the same comparison the fork's "v4 is v3 plus the shadow" test makes.
+    let source_rule_v4 = class.era.is_some()
+        && matches!(class.shadow, Some(ShadowClass { instrs: V4_SHADOW_INSTRS, .. }))
+        && LoadClass { era: None, shadow: None, ..class } == LoadClass { shadow: None, ..V4_CLASS };
     let mut fresh = [false; 8];
     let mut entropy_kept = [false; 8];
     let mut instrs = Vec::with_capacity(INSTR_COUNT);