diff --git a/src/app/utils/propertyFilters.ts b/src/app/utils/propertyFilters.ts
index 56b178a6..27b4f09a 100644
--- a/src/app/utils/propertyFilters.ts
+++ b/src/app/utils/propertyFilters.ts
@@ -269,8 +269,10 @@ export const HEATING_SYSTEM_OPTIONS: DescriptorBucket[] = [
   { label: "Community",        needles: ["community"] },
   { label: "Solid Fuel",       needles: ["coal", "anthracite", "smokeless", "wood", "dual fuel", "biomass", "solid fuel"] },
   // NB: bare "oil" is a substring of "b(oil)er" — match the fuel token only (", oil"
-  // as in "Boiler and radiators, oil") and the leading override "Oil room heater".
-  { label: "Oil",              needles: [", oil", "oil room heater"] },
+  // as in "Boiler and radiators, oil") and the leading override vocabulary
+  // ("Oil room heater …", "Oil boiler, regular/combi"). "oil boiler" cannot
+  // collide with "solid fuel boiler", and Solid Fuel is checked first regardless.
+  { label: "Oil",              needles: [", oil", "oil room heater", "oil boiler"] },
   { label: "LPG",              needles: ["lpg"] },
   { label: "Gas Room Heater",  needles: ["gas room heater", "room heaters, mains gas", "room heaters, gas"] },
   { label: "Gas Boiler",       needles: ["mains gas", "gas boiler", "gas cpsu"] },
diff --git a/src/lib/services/descriptorResolution.test.ts b/src/lib/services/descriptorResolution.test.ts
index 1c487586..844b3920 100644
--- a/src/lib/services/descriptorResolution.test.ts
+++ b/src/lib/services/descriptorResolution.test.ts
@@ -507,6 +507,20 @@ describe("classifyDescriptor — wall / roof / heating buckets", () => {
     expect(heat("Boiler and radiators, dual fuel (mineral and wood)")).toBe("Solid Fuel");
     expect(heat("Boiler and radiators, lpg")).toBe("LPG");
   });
+
+  // The non-gas wet-boiler archetypes: their fuel leads the string rather than
+  // following a comma, so they are the case the ", oil" needle cannot catch.
+  // Asserted by bucket rather than just "not Unknown", because the failure mode
+  // that matters is a *wrong* bucket — reorder the needles and "Oil boiler,
+  // combi" silently becomes a Gas Boiler, which the coverage test would pass.
+  it("buckets the non-gas wet-boiler override archetypes by their fuel", () => {
+    expect(heat("Oil boiler, regular")).toBe("Oil");
+    expect(heat("Oil boiler, combi")).toBe("Oil");
+    expect(heat("Solid fuel boiler")).toBe("Solid Fuel");
+    // Guard the collision the "oil boiler" needle could have caused: Solid Fuel
+    // is checked first, and a gas boiler still has no "oil" fuel token.
+    expect(heat("Gas boiler, combi")).toBe("Gas Boiler");
+  });
 });
 
 /** Legacy-property helper: only year_built is set, cutoff is false. */