diff --git a/src/LibHac/HashHelpers.cs b/src/LibHac/HashHelpers.cs
index b30778a6..06d29deb 100644
--- a/src/LibHac/HashHelpers.cs
+++ b/src/LibHac/HashHelpers.cs
@@ -52,40 +52,20 @@ namespace LibHac
             return (candidate == 2);
         }
 
-        public static int GetHashTableEntryCount(int entries)
-        {
-            uint count = (uint) entries;
-            if (entries < 3)
-                count = 3;
-            else if (count < 19)
-                count |= 1;
-            else
-            {
-                while (count % 2 == 0 || count % 3 == 0 || count % 5 == 0 || count % 7 == 0 || count % 11 == 0 || count % 13 == 0 || count % 17 == 0)
-                {
-                    count++;
-                }
-            }
-            return (int) count;
-        }
-
         public static int GetPrime(int min)
         {
             if (min < 0)
                 throw new ArgumentException(nameof(min));
 
-            // RomFS dictionaries choose from all possible primes
-
-            //for (int i = 0; i < Primes.Length; i++)
-            //{
-            //    int prime = Primes[i];
-            //    if (prime >= min)
-            //        return prime;
-            //}
+            for (int i = 0; i < Primes.Length; i++)
+            {
+                int prime = Primes[i];
+                if (prime >= min)
+                    return prime;
+            }
 
             //outside of our predefined table. 
             //compute the hard way. 
-
             for (int i = (min | 1); i < int.MaxValue; i += 2)
             {
                 if (IsPrime(i) && ((i - 1) % HashPrime != 0))
@@ -109,5 +89,19 @@ namespace LibHac
 
             return GetPrime(newSize);
         }
+
+        public static int GetRomFsPrime(int min)
+        {
+            if (min < 3) return 3;
+            if (min < 19) return min | 1;
+
+            for (int i = (min | 1); i < int.MaxValue; i += 2)
+            {
+                if (i % 2 != 0 && i % 3 != 0 && i % 5 != 0 && i % 7 != 0 && i % 11 != 0 && i % 13 != 0 && i % 17 != 0)
+                    return i;
+            }
+
+            return min;
+        }
     }
 }
\ No newline at end of file
diff --git a/src/LibHac/IO/RomFs/HierarchicalRomFileTable.cs b/src/LibHac/IO/RomFs/HierarchicalRomFileTable.cs
index d47549d3..43e998da 100644
--- a/src/LibHac/IO/RomFs/HierarchicalRomFileTable.cs
+++ b/src/LibHac/IO/RomFs/HierarchicalRomFileTable.cs
@@ -27,6 +27,8 @@ namespace LibHac.IO.RomFs
             DirectoryTable = new RomFsDictionary<DirectoryRomEntry>(DirHashTableStorage, DirEntryTableStorage);
         }
 
+        public HierarchicalRomFileTable() : this(0, 0) { }
+
         public HierarchicalRomFileTable(int directoryCapacity, int fileCapacity)
         {
             FileTable = new RomFsDictionary<FileRomEntry>(fileCapacity);
@@ -155,6 +157,12 @@ namespace LibHac.IO.RomFs
             CreateDirectoryRecursive(GetUtf8Bytes(path));
         }
 
+        public void TrimExcess()
+        {
+            DirectoryTable.TrimExcess();
+            FileTable.TrimExcess();
+        }
+
         private static ReadOnlySpan<byte> GetUtf8Bytes(string value)
         {
             return Encoding.UTF8.GetBytes(value).AsSpan();
diff --git a/src/LibHac/IO/RomFs/RomFsBuilder.cs b/src/LibHac/IO/RomFs/RomFsBuilder.cs
index aa6f671e..09dfde59 100644
--- a/src/LibHac/IO/RomFs/RomFsBuilder.cs
+++ b/src/LibHac/IO/RomFs/RomFsBuilder.cs
@@ -16,17 +16,14 @@ namespace LibHac.IO.RomFs
 
         public RomFsBuilder(IFileSystem input)
         {
-            DirectoryEntry[] entries = input.EnumerateEntries().ToArray();
-            int fileCount = entries.Count(x => x.Type == DirectoryEntryType.File);
-            int dirCount = entries.Count(x => x.Type == DirectoryEntryType.Directory);
-
-            FileTable = new HierarchicalRomFileTable(dirCount, fileCount);
+            FileTable = new HierarchicalRomFileTable();
+            var fileInfo = new RomFileInfo();
 
             long offset = 0;
 
-            foreach (DirectoryEntry file in entries.Where(x => x.Type == DirectoryEntryType.File).OrderBy(x => x.FullPath, StringComparer.Ordinal))
+            foreach (DirectoryEntry file in input.EnumerateEntries().Where(x => x.Type == DirectoryEntryType.File)
+                .OrderBy(x => x.FullPath, StringComparer.Ordinal))
             {
-                var fileInfo = new RomFileInfo();
                 fileInfo.Offset = offset;
                 fileInfo.Length = file.Size;
 
@@ -41,6 +38,8 @@ namespace LibHac.IO.RomFs
 
                 FileTable.CreateFile(file.FullPath, ref fileInfo);
             }
+
+            FileTable.TrimExcess();
         }
 
         public IStorage Build()
diff --git a/src/LibHac/IO/RomFs/RomFsDictionary.cs b/src/LibHac/IO/RomFs/RomFsDictionary.cs
index 18b80dd9..007a275e 100644
--- a/src/LibHac/IO/RomFs/RomFsDictionary.cs
+++ b/src/LibHac/IO/RomFs/RomFsDictionary.cs
@@ -27,9 +27,11 @@ namespace LibHac.IO.RomFs
             _count = CountEntries();
         }
 
+        public RomFsDictionary() : this(0) { }
+
         public RomFsDictionary(int capacity)
         {
-            int size = HashHelpers.GetHashTableEntryCount(capacity);
+            int size = HashHelpers.GetRomFsPrime(capacity);
 
             Buckets = new int[size];
             Buckets.AsSpan().Fill(-1);
@@ -83,7 +85,7 @@ namespace LibHac.IO.RomFs
         public int Add(ref RomEntryKey key, ref T value)
         {
             ref T entry = ref AddOrGet(ref key, out int offset, out bool alreadyExists, out _);
-            
+
             if (alreadyExists)
             {
                 throw new ArgumentException("Key already exists in dictionary.");
@@ -124,6 +126,12 @@ namespace LibHac.IO.RomFs
                 Buckets[bucket] = newOffset;
                 _count++;
 
+                if (Buckets.Length < _count)
+                {
+                    Resize();
+                    entry = ref GetEntryReference(newOffset, out name, key.Name.Length);
+                }
+
                 return ref entry.Value;
             }
         }
@@ -210,7 +218,9 @@ namespace LibHac.IO.RomFs
             return count;
         }
 
-        public void Resize(int newSize)
+        private void Resize() => Resize(HashHelpers.ExpandPrime(_count));
+
+        private void Resize(int newSize)
         {
             var newBuckets = new int[newSize];
             newBuckets.AsSpan().Fill(-1);
@@ -231,6 +241,12 @@ namespace LibHac.IO.RomFs
             Buckets = newBuckets;
         }
 
+        public void TrimExcess()
+        {
+            Resize(HashHelpers.GetRomFsPrime(_count));
+            SetCapacity(_length);
+        }
+
         private ref RomFsEntry GetEntryReference(int offset)
         {
             return ref MemoryMarshal.Cast<byte, RomFsEntry>(Entries.AsSpan(offset))[0];