PaperMC/nms-patches/ItemSnowball.patch

--- a/net/minecraft/server/ItemSnowball.java
+++ b/net/minecraft/server/ItemSnowball.java
@@ -8,17 +8,28 @@
     }
 
     public InteractionResultWrapper<ItemStack> a(ItemStack itemstack, World world, EntityHuman entityhuman, EnumHand enumhand) {
-        if (!entityhuman.abilities.canInstantlyBuild) {
+        // CraftBukkit start - moved down
+        /*if (!entityhuman.abilities.canInstantlyBuild) {
             --itemstack.count;
         }
 
         world.a((EntityHuman) null, entityhuman.locX, entityhuman.locY, entityhuman.locZ, SoundEffects.fS, SoundCategory.NEUTRAL, 0.5F, 0.4F / (ItemSnowball.j.nextFloat() * 0.4F + 0.8F));
+        */
         if (!world.isClientSide) {
             EntitySnowball entitysnowball = new EntitySnowball(world, entityhuman);
 
             entitysnowball.a(entityhuman, entityhuman.pitch, entityhuman.yaw, 0.0F, 1.5F, 1.0F);
-            world.addEntity(entitysnowball);
+            if (world.addEntity(entitysnowball)) {
+                if (!entityhuman.abilities.canInstantlyBuild) {
+                    --itemstack.count;
+                }
+
+                world.a((EntityHuman) null, entityhuman.locX, entityhuman.locY, entityhuman.locZ, SoundEffects.fS, SoundCategory.NEUTRAL, 0.5F, 0.4F / (ItemSnowball.j.nextFloat() * 0.4F + 0.8F));
+            } else if (entityhuman instanceof EntityPlayer) {
+                ((EntityPlayer) entityhuman).getBukkitEntity().updateInventory();
+            }
         }
+        // CraftBukkit end
 
         entityhuman.b(StatisticList.b((Item) this));
         return new InteractionResultWrapper(EnumInteractionResult.SUCCESS, itemstack);