diff --git a/src/main/lemondronor/circlebot/generation.cljc b/src/main/lemondronor/circlebot/generation.cljc
index 865cacc..de89e67 100644
--- a/src/main/lemondronor/circlebot/generation.cljc
+++ b/src/main/lemondronor/circlebot/generation.cljc
@@ -68,7 +68,9 @@
 (def filters
   {:a-an (fn a-an [s]
            (if (starts-with-consonant? s)
-             (str "a " s)
+             (if (re-find #"^[FHLMNRSX](\b|[A-Z0-9])" s)
+               (str "an " s)
+               (str "a " s))
              (str "an " s)))})
 
 
diff --git a/src/test/lemondronor/circlebot/generation_test.cljs b/src/test/lemondronor/circlebot/generation_test.cljs
index 0637b05..c0c8307 100644
--- a/src/test/lemondronor/circlebot/generation_test.cljs
+++ b/src/test/lemondronor/circlebot/generation_test.cljs
@@ -1,5 +1,5 @@
 (ns lemondronor.circlebot.generation-test
-  (:require [cljs.test :refer (deftest is)]
+  (:require [cljs.test :refer (deftest is testing)]
             [lemondronor.circlebot.generation :as generation]))
 
 (deftest parse-template
@@ -27,7 +27,7 @@
          (generation/generate-all
           [(generation/parse-template "Hello!")]
           {})))
-    (is (= "Hello!"
+  (is (= "Hello!"
          (generation/generate
           [(generation/parse-template "Hello!")]
           {}))))
@@ -74,15 +74,26 @@
 
 
 (deftest filters
-  (let [templates [(generation/parse-template "It is {thing|a-an}")]]
-    (is (= "It is a bird"
-           (generation/generate templates {:thing "bird"})))
-    (is (= "It is an animal"
-           (generation/generate templates {:thing "animal"})))
-    (is (= "It is an Animal"
-           (generation/generate templates {:thing "Animal"})))
-    (is (= "It is a Eurocopter"
-           (generation/generate templates {:thing "Eurocopter"})))))
+  (testing "a-an"
+    (let [templates [(generation/parse-template "It is {thing|a-an}")]]
+      (is (= "It is a bird"
+             (generation/generate templates {:thing "bird"})))
+      (is (= "It is an animal"
+             (generation/generate templates {:thing "animal"})))
+      (is (= "It is an Animal"
+             (generation/generate templates {:thing "Animal"})))
+      (is (= "It is a Eurocopter"
+             (generation/generate templates {:thing "Eurocopter"})))
+      (is (= "It is an MD-500"
+             (generation/generate templates {:thing "MD-500"})))
+      (is (= "It is an F-15"
+             (generation/generate templates {:thing "F-15"})))
+      (is (= "It is an X-15"
+             (generation/generate templates {:thing "X-15"})))
+      (is (= "It is a KXL-10"
+             (generation/generate templates {:thing "KXL-10"})))
+
+      )))
 
 ;; (deftest var-paths
 ;;   (is (= "Hello, John"