1 files changed, 9 insertions, 2 deletions
diff --git a/src/find-reverse.js b/src/find-reverse.js
index f31d3c45..c99a4a71 100644
--- a/src/find-reverse.js
+++ b/src/find-reverse.js
@@ -11,16 +11,23 @@ export function getAllSpecs({
 }) {
   try {
     thingConstructors;
-  } catch (error) {
+  } catch {
     throw new Error(`Thing constructors aren't ready yet, can't get all ${word} specs`);
   }
 
   const specs = {...hardcodedSpecs};
 
+  const seenSpecs = new Set();
+
   for (const thingConstructor of Object.values(thingConstructors)) {
     const thingSpecs = thingConstructor[constructorKey];
     if (!thingSpecs) continue;
 
+    // Subclasses can expose literally the same static properties
+    // by inheritence. We don't want to double-count those!
+    if (seenSpecs.has(thingSpecs)) continue;
+    seenSpecs.add(thingSpecs);
+
     for (const [key, spec] of Object.entries(thingSpecs)) {
       specs[key] =
         postprocessSpec(spec, {
@@ -45,7 +52,7 @@ export function findSpec(key, {
 
   try {
     thingConstructors;
-  } catch (error) {
+  } catch {
     throw new Error(`Thing constructors aren't ready yet, can't check if "${word}.${key}" available`);
   }