diff --git a/lib/keisan/context.rb b/lib/keisan/context.rb
index 164c471..b7b6362 100644
--- a/lib/keisan/context.rb
+++ b/lib/keisan/context.rb
@@ -111,7 +111,11 @@ def register_function!(name, function, local: false)
     end
 
     def random
-      @random || @parent&.random || Random.new
+      @random ||= @parent&.random || Random.new
+    end
+
+    def set_random(random)
+      @random = random
     end
 
     protected
diff --git a/lib/keisan/version.rb b/lib/keisan/version.rb
index 25776be..c6726a0 100644
--- a/lib/keisan/version.rb
+++ b/lib/keisan/version.rb
@@ -1,3 +1,3 @@
 module Keisan
-  VERSION = "0.8.6"
+  VERSION = "0.8.7"
 end
diff --git a/spec/keisan/context_spec.rb b/spec/keisan/context_spec.rb
index 311d3c1..f5ef08d 100644
--- a/spec/keisan/context_spec.rb
+++ b/spec/keisan/context_spec.rb
@@ -166,6 +166,25 @@
 
       expect(matches.any? {|bool| bool == false}).to be true
     end
+
+    it "has the random object set once and only once" do
+      context = described_class.new
+      random = context.random
+      expect(random).to eq context.random
+    end
+
+    it "can be set to override existing internal random object" do
+      rand1 = Random.new(2244)
+      rand1_copy = Random.new(2244)
+      rand2 = Random.new(4466)
+
+      context = described_class.new(random: rand2)
+      context.set_random(rand1_copy)
+
+      20.times do
+        expect(context.random.rand(100)).to eq rand1.rand(100)
+      end
+    end
   end
 
   describe "has_variable?" do
diff --git a/spec/version_spec.rb b/spec/version_spec.rb
index 0f1dd24..fcee67a 100644
--- a/spec/version_spec.rb
+++ b/spec/version_spec.rb
@@ -2,6 +2,6 @@
 
 RSpec.describe Keisan do
   it "has the expected version number" do
-    expect(Keisan::VERSION).to eq "0.8.6"
+    expect(Keisan::VERSION).to eq "0.8.7"
   end
 end