diff --git a/spec/minisign/nacl_spec.rb b/spec/minisign/nacl_spec.rb
new file mode 100644
index 0000000..e2cdfbc
--- /dev/null
+++ b/spec/minisign/nacl_spec.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+describe Minisign::NaCl do
+  it 'raises LibSodiumDependencyErro if libsodium not installed' do
+    hash = RbNaCl.send(:remove_const, :Hash)
+    expect do
+      Minisign::NaCl::Hash::Blake2b.digest('message', { digest_size: 32 })
+    end.to raise_error(Minisign::LibSodiumDependencyError)
+    RbNaCl.const_set(:Hash, hash)
+  end
+end