diff --git a/src/js/extendedFamilyModeJS.js b/src/js/extendedFamilyModeJS.js
index efc4fab6e0872a5ec9f46b6cbdb09e86b84a1a6d..34159b977d15c480b5bdf1b1cc34236fe91b9c24 100644
--- a/src/js/extendedFamilyModeJS.js
+++ b/src/js/extendedFamilyModeJS.js
@@ -403,7 +403,7 @@ window.relativeTerm =
 			return "mother";
 		} else if (slave1.father === slave2.ID) {
 			return "father";
-		} else if (areSisters(slave2, slave1) == 1) {
+		} else if (areSisters(slave2, slave1) === 1) {
 			if (slave2.genes === "XY" && State.variables.diversePronouns) {
 				return "twin brother";
 			} else {