PaperMC/paper-server/patches/sources/net/minecraft/world/entity/AgeableMob.java.patch

--- a/net/minecraft/world/entity/AgeableMob.java
+++ b/net/minecraft/world/entity/AgeableMob.java
@@ -21,6 +21,7 @@
     protected int age;
     protected int forcedAge;
     protected int forcedAgeTimer;
+    public boolean ageLocked; // CraftBukkit
 
     protected AgeableMob(EntityType<? extends AgeableMob> type, Level world) {
         super(type, world);
@@ -104,6 +105,7 @@
         super.addAdditionalSaveData(nbt);
         nbt.putInt("Age", this.getAge());
         nbt.putInt("ForcedAge", this.forcedAge);
+        nbt.putBoolean("AgeLocked", this.ageLocked); // CraftBukkit
     }
 
     @Override
@@ -111,6 +113,7 @@
         super.readAdditionalSaveData(nbt);
         this.setAge(nbt.getInt("Age"));
         this.forcedAge = nbt.getInt("ForcedAge");
+        this.ageLocked = nbt.getBoolean("AgeLocked"); // CraftBukkit
     }
 
     @Override
@@ -125,7 +128,7 @@
     @Override
     public void aiStep() {
         super.aiStep();
-        if (this.level().isClientSide) {
+        if (this.level().isClientSide || this.ageLocked) { // CraftBukkit
             if (this.forcedAgeTimer > 0) {
                 if (this.forcedAgeTimer % 4 == 0) {
                     this.level().addParticle(ParticleTypes.HAPPY_VILLAGER, this.getRandomX(1.0D), this.getRandomY() + 0.5D, this.getRandomZ(1.0D), 0.0D, 0.0D, 0.0D);