diff --git a/gerbil-manager-web/src/genetics/__tests__/genetics.test.ts b/gerbil-manager-web/src/genetics/__tests__/genetics.test.ts
index 1cee92c..b6b650b 100644
--- a/gerbil-manager-web/src/genetics/__tests__/genetics.test.ts
+++ b/gerbil-manager-web/src/genetics/__tests__/genetics.test.ts
@@ -379,3 +379,23 @@ describe('GEN-3c: no Unbekannt when the E locus is known (family fallback)', ()
     expect(farbschlagFor(fromDisplayString('aa C- DD EE GG PP spsp rere')).unknown).toBe(false)
   })
 })
+
+describe('GEN-3d: dominance tiebreak for unknown loci', () => {
+  it('unknown-C reads as full-colour, NOT a c^h/c^chm white', () => {
+    // 'aa C- DD EE GG PP' -> Schwarz (dominant C reading), never PEW/Hermelin/Himalaya.
+    const name = genotypeToFarbschlag(fromDisplayString('aa C- DD EE GG PP spsp rere'))
+    expect(name).toBe('Schwarz')
+    expect(['Pink Eyed White (PEW)', 'Hermelin', 'Himalaya']).not.toContain(name)
+  })
+
+  it('unknown second marker allele defaults UNMARKED, not Schecke (marker-aware)', () => {
+    // 'sp-' (one sp + unknown) -> sp/sp -> no Schecke (naive most-dominant would wrongly add it).
+    expect(genotypeToFarbschlag(fromDisplayString('AA CC DD EE GG PP sp- rere'))).toBe('Agouti')
+  })
+
+  it('still: eef with unknowns -> Fuchsschimmel (family pin unaffected by tiebreak)', () => {
+    expect(genotypeToFarbschlag(fromDisplayString('aa C- D- eef Gg Pp spsp --'))).toBe(
+      'Fuchsschimmel',
+    )
+  })
+})
diff --git a/gerbil-manager-web/src/genetics/catalog.ts b/gerbil-manager-web/src/genetics/catalog.ts
index 360f056..0c2e468 100644
--- a/gerbil-manager-web/src/genetics/catalog.ts
+++ b/gerbil-manager-web/src/genetics/catalog.ts
@@ -20,7 +20,7 @@
  *    meta rows dropped, 17 matched the frozen names). Genotypes normalized from
  *    portal notation (c[chm]->cchm, c[h]->ch, e[f]->ef, '-'/'--' = unknown).
  */
-import { LOCUS_ORDER, dominantAllele, type LocusKey } from './loci'
+import { LOCI, LOCUS_ORDER, dominantAllele, type LocusKey } from './loci'
 import {
   makeGenotype,
   toDisplayString,
@@ -145,13 +145,22 @@ export interface FarbschlagMatch {
 }
 
 /**
- * Expressed token at a locus, or null when UNKNOWN (a '?' allele) — null acts as
- * a wildcard in matching. The E locus is PAIR-aware so the Fuchs/Schimmel family
- * is distinguishable: ee->'e', e/ef->'eef' (Fuchsschimmel), ef/ef->'ef' (Schimmel).
+ * Expressed token at a locus. GEN-3d: an UNKNOWN allele ('?') is resolved to the
+ * MOST-DOMINANT allele of the locus (the safer default) rather than acting as a
+ * match-anything wildcard — so an unknown-C animal reads as full-colour 'C', not
+ * a c^h/c^chm colourpoint white. The E locus stays PAIR-aware so the Fuchs/
+ * Schimmel family is distinguishable: ee->'e', e/ef->'eef', ef/ef->'ef'.
+ * (The Fuchs/Schimmel FAMILY for unknown-E is still handled by eFamily on the
+ * raw pair, which runs before this.)
  */
-function locusToken(g: Genotype, locus: LocusKey): string | null {
-  const [x, y] = g[locus]
-  if (x === WILDCARD || y === WILDCARD) return null
+function locusToken(g: Genotype, locus: LocusKey): string {
+  // Default an unknown allele to the WILD-TYPE reading: most-dominant for the
+  // colour loci (unknown-C => full-colour 'C', not a white), but the recessive
+  // UNMARKED allele for the spotting/rex markers (unknown-Sp must NOT imply Schecke).
+  const alleles = LOCI[locus].alleles
+  const isMarker = locus === 'Sp' || locus === 'Re' || locus === 'Sls'
+  const fallback = isMarker ? alleles[alleles.length - 1] : alleles[0]
+  const [x, y] = g[locus].map((a) => (a === WILDCARD ? fallback : a))
   if (locus === 'E') {
     if (x === y) return x // ee->'e', efef->'ef', EE->'E'
     if ((x === 'e' && y === 'ef') || (x === 'ef' && y === 'e')) return 'eef'
@@ -161,11 +170,9 @@ function locusToken(g: Genotype, locus: LocusKey): string | null {
 }
 
 function matches(g: Genotype, entry: FarbschlagEntry): boolean {
-  // Unknown loci (null token) match anything (treated as wildcard, GEN-3c).
-  return (Object.keys(entry.tokens) as LocusKey[]).every((locus) => {
-    const t = locusToken(g, locus)
-    return t === null || t === entry.tokens[locus]
-  })
+  return (Object.keys(entry.tokens) as LocusKey[]).every(
+    (locus) => locusToken(g, locus) === entry.tokens[locus],
+  )
 }
 
 /**