diff --git a/engine/src/main/java/org/terasology/engine/config/SystemConfig.java b/engine/src/main/java/org/terasology/engine/config/SystemConfig.java
index 9f0aafd1ab6..006d160a593 100644
--- a/engine/src/main/java/org/terasology/engine/config/SystemConfig.java
+++ b/engine/src/main/java/org/terasology/engine/config/SystemConfig.java
@@ -8,9 +8,14 @@
 import org.terasology.engine.config.flexible.constraints.LocaleConstraint;
 import org.terasology.engine.config.flexible.constraints.NumberRangeConstraint;
 
+import java.util.Arrays;
 import java.util.Locale;
 import java.util.Locale.Category;
 import java.util.Optional;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static java.lang.Math.max;
 import static org.terasology.engine.config.flexible.SettingArgument.constraint;
@@ -81,13 +86,34 @@ public class SystemConfig extends AutoConfig {
 
     public final Setting<Locale> locale = setting(
             type(Locale.class),
-            defaultValue(Locale.getDefault(Category.DISPLAY)),
+            defaultValue(getAdjustedLocale()),
             name("${engine:menu#settings-language}"),
-            constraint(new LocaleConstraint(Locale.getAvailableLocales())) // TODO provide translate project's locales (Pirate lang don't works)
+            constraint(new LocaleConstraint(
+                // Locale.getAvailableLocales() + non-standard "pr" (pirate) tag
+                Stream.concat(Arrays.stream(Locale.getAvailableLocales()), Stream.of(Locale.forLanguageTag("pr")))
+                .collect(Collectors.toSet())))
     );
 
     @Override
     public String getName() {
         return "${engine:menu#system-settings-title}";
     }
+
+    private static Locale getAdjustedLocale() {
+        Locale systemLocale = Locale.getDefault(Category.DISPLAY);
+
+        // Matches unusual locales on Mac OS created from the user's language and location, e.g. en_UA
+        if (!Arrays.asList(Locale.getAvailableLocales()).contains(systemLocale)) {
+            final Pattern langRegionPattern = Pattern.compile("[a-z]{2}_[A-Z]{2}");
+
+            String input = systemLocale.toString();
+            Matcher matcher = langRegionPattern.matcher(input);
+
+            // If the locale is like that, convert it to just the language, e.g. en_UA -> en
+            if (matcher.find()) {
+                systemLocale = Locale.forLanguageTag(systemLocale.getLanguage());
+            }
+        }
+        return systemLocale;
+    }
 }