diff --git a/lib/pry/commands/watch_expression.rb b/lib/pry/commands/watch_expression.rb
index ee28a1b1..05d8e36e 100644
--- a/lib/pry/commands/watch_expression.rb
+++ b/lib/pry/commands/watch_expression.rb
@@ -38,7 +38,7 @@ class Pry
     private
 
     def expressions
-      state.expressions ||= []
+      Pry.config.watch_expressions ||= []
     end
 
     def delete(index)
@@ -66,7 +66,7 @@ class Pry
       end
     end
 
-    def eval_and_print_changed
+    def eval_and_print_changed(output)
       expressions.each do |expr|
         expr.eval!
         if expr.changed?
@@ -82,9 +82,9 @@ class Pry
 
     def add_hook
       hook = [:after_eval, :watch_expression]
-      unless Pry.config.hooks.hook_exists?(*hook)
-        _pry_.hooks.add_hook(*hook) do
-          eval_and_print_changed
+      unless Pry.hooks.hook_exists?(*hook)
+        Pry.hooks.add_hook(*hook) do |_, _pry_|
+          eval_and_print_changed _pry_.output
         end
       end
     end
diff --git a/spec/commands/watch_expression_spec.rb b/spec/commands/watch_expression_spec.rb
index 4801bdb3..e87d8be4 100644
--- a/spec/commands/watch_expression_spec.rb
+++ b/spec/commands/watch_expression_spec.rb
@@ -64,6 +64,30 @@ describe "watch expression" do
     end
   end
 
+  it "continues to work if you start a second pry instance" do
+    ReplTester.start do
+      input 'a = 1'
+      output '=> 1'
+
+      input 'watch a'
+      output "Watching a\nwatch: a => 1"
+
+      input "a = 2"
+      output "watch: a => 2\n=> 2"
+    end
+
+    ReplTester.start do
+      input 'b = 1'
+      output '=> 1'
+
+      input 'watch b'
+      output "Watching b\nwatch: b => 1"
+
+      input "b = 2"
+      output "watch: b => 2\n=> 2"
+    end
+  end
+
   describe "deleting expressions" do
     before do
       eval 'watch :keeper'