diff --git a/CHANGELOG.md b/CHANGELOG.md
index bf42e3268..c4ea50fdb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#1893](https://github.com/ruby-grape/grape/pull/1893): Allows `Grape::API` to behave like a Rack::app in some instances where it was misbehaving - [@myxoh](https://github.com/myxoh).
 
 ### 1.2.4 (2019/06/13)
 
diff --git a/lib/grape/api.rb b/lib/grape/api.rb
index d4b70ae3e..a830bb834 100644
--- a/lib/grape/api.rb
+++ b/lib/grape/api.rb
@@ -48,7 +48,12 @@ def override_all_methods!
       # (http://www.rubydoc.info/github/rack/rack/master/file/SPEC) for more.
       # NOTE: This will only be called on an API directly mounted on RACK
       def call(*args, &block)
-        base_instance.call(*args, &block)
+        instance_for_rack = if never_mounted?
+                              base_instance
+                            else
+                              mounted_instances.first
+                            end
+        instance_for_rack.call(*args, &block)
       end
 
       # Allows an API to itself be inheritable:
@@ -147,6 +152,14 @@ def evaluate_arguments(configuration, *args)
           end
         end
       end
+
+      def never_mounted?
+        mounted_instances.empty?
+      end
+
+      def mounted_instances
+        instances - [base_instance]
+      end
     end
   end
 end
diff --git a/spec/grape/integration/rack_spec.rb b/spec/grape/integration/rack_spec.rb
index e7c9f5665..a1e49a6d8 100644
--- a/spec/grape/integration/rack_spec.rb
+++ b/spec/grape/integration/rack_spec.rb
@@ -31,4 +31,26 @@
       input.unlink
     end
   end
+
+  context 'when the app is mounted' do
+    def app
+      @main_app ||= Class.new(Grape::API) do
+        get 'ping'
+      end
+    end
+
+    let!(:base) do
+      app_to_mount = app
+      Class.new(Grape::API) do
+        namespace 'namespace' do
+          mount app_to_mount
+        end
+      end
+    end
+
+    it 'finds the app on the namespace' do
+      get '/namespace/ping'
+      expect(last_response.status).to eq 200
+    end
+  end
 end