diff --git a/src/classes.js b/src/classes.js
index 5798aac4e..e07f345dc 100644
--- a/src/classes.js
+++ b/src/classes.js
@@ -46,7 +46,7 @@ export class Example {
 
     requiredMorphemesPresent(pronoun, counter = 0) {
         return this.parts(pronoun, counter).filter(part => part.variable)
-            .every(part => pronoun.getMorpheme(part.str, counter) != null);
+            .every(part => pronoun.getMorpheme(part.str, counter) !== null);
     }
 
     format(pronoun) {
@@ -400,6 +400,9 @@ export class Pronoun {
         const options = this.morphemes[morpheme].split('&');
 
         const result = options[counter % options.length];
+        if (result === '') {
+            return null;
+        }
 
         return capital ? capitalise(result) : result;
     }