diff --git a/package-set.dhall b/package-set.dhall
index 4efcd31..325bbc2 100644
--- a/package-set.dhall
+++ b/package-set.dhall
@@ -4,8 +4,8 @@ let Package = { name : Text, version : Text, repo : Text, dependencies : List Te
 let additions = [
   { name = "io"
   , repo = "https://github.com/aviate-labs/io.mo"
-  , version = "v0.3.0"
-  , dependencies = ["base"]
+  , version = "v0.3.1"
+  , dependencies = [ "base" ]
   }
 ] : List Package
 
diff --git a/src/LFSR.mo b/src/LFSR.mo
index 22babe5..42d8609 100644
--- a/src/LFSR.mo
+++ b/src/LFSR.mo
@@ -1,4 +1,4 @@
-import Array "mo:base/Array";
+import Buffer "mo:base/Buffer";
 import Int "mo:base/Int";
 import IO "mo:io/IO";
 import Iter "mo:base/Iter";
@@ -94,14 +94,14 @@ module {
         let lfsr = feed;
         var restarted = false;
         public func read(n : Nat) : IO.Result<[T]> {
-            var ts : [T] = [];
+            let ts = Buffer.Buffer<T>(n);
             for (i in Iter.range(0, n-1)) {
-                if (restarted) return #eof(ts);
+                if (restarted) return #eof(ts.toArray());
                 let (v, r) = lfsr.next();
                 restarted := r;
-                ts := Array.append<T>(ts, [v]);
+                ts.add(v);
             };
-            #ok(ts);
+            #ok(ts.toArray());
         };
     };
 
diff --git a/src/XorShift.mo b/src/XorShift.mo
index 7d5b901..089d7d1 100644
--- a/src/XorShift.mo
+++ b/src/XorShift.mo
@@ -1,4 +1,3 @@
-import Array "mo:base/Array";
 import Binary "mo:encoding/Binary";
 import Buffer "mo:base/Buffer";
 import Int "mo:base/Int";
@@ -40,7 +39,7 @@ module {
         let xors = gen;
         let bs = Buffer.Buffer<Nat8>(8);
         public func read(n : Nat) : IO.Result<[Nat8]> {
-            var ts : [Nat8] = [];
+            let ts = Buffer.Buffer<Nat8>(n);
             for (_ in Iter.range(0, n-1)) {
                 if (bs.size() == 0) {
                     for (b in Binary.BigEndian.fromNat64(gen.next()).vals()) {
@@ -49,12 +48,12 @@ module {
                 };
                 switch (bs.removeLast()) {
                     case (? v) {
-                        ts := Array.append<Nat8>(ts, [v]);
+                        ts.add(v);
                     };
-                    case (null) return #eof(ts);
+                    case (null) return #eof(ts.toArray());
                 };
             };
-            #ok(ts);
+            #ok(ts.toArray());
         };
     };
 };