diff --git a/ruby/ql/lib/codeql/ruby/frameworks/Rack.qll b/ruby/ql/lib/codeql/ruby/frameworks/Rack.qll
index ec3673207ac..503af8e8533 100644
--- a/ruby/ql/lib/codeql/ruby/frameworks/Rack.qll
+++ b/ruby/ql/lib/codeql/ruby/frameworks/Rack.qll
@@ -2,6 +2,7 @@
  * Provides modeling for the Rack library.
  */
 
+private import codeql.ruby.Concepts
 private import codeql.ruby.controlflow.CfgNodes::ExprNodes
 private import codeql.ruby.DataFlow
 private import codeql.ruby.typetracking.TypeTracker
@@ -17,48 +18,63 @@ module Rack {
    */
   class AppCandidate extends DataFlow::ClassNode {
     private DataFlow::MethodNode call;
+    private PotentialResponseNode resp;
 
     AppCandidate() {
       call = this.getInstanceMethod("call") and
       call.getNumberOfParameters() = 1 and
-      call.getReturn() = trackRackResponse()
+      call.getReturn() = trackRackResponse(resp)
     }
 
     /**
      * Gets the environment of the request, which is the lone parameter to the `call` method.
      */
     DataFlow::ParameterNode getEnv() { result = call.getParameter(0) }
+
+    /** Gets the response returned from the request. */
+    PotentialResponseNode getResponse() { result = resp }
   }
 
-  private DataFlow::LocalSourceNode trackStatusCode(TypeTracker t, int i) {
+  private DataFlow::LocalSourceNode trackInt(TypeTracker t, int i) {
     t.start() and
     result.getConstantValue().isInt(i)
     or
-    exists(TypeTracker t2 | result = trackStatusCode(t2, i).track(t2, t))
+    exists(TypeTracker t2 | result = trackInt(t2, i).track(t2, t))
   }
 
-  private DataFlow::Node trackStatusCode(int i) {
-    trackStatusCode(TypeTracker::end(), i).flowsTo(result)
-  }
+  private DataFlow::Node trackInt(int i) { trackInt(TypeTracker::end(), i).flowsTo(result) }
 
-  class ResponseNode extends DataFlow::ArrayLiteralNode {
+  private class PotentialResponseNode extends DataFlow::ArrayLiteralNode {
     // [status, headers, body]
-    ResponseNode() { this.getNumberOfArguments() = 3 }
+    PotentialResponseNode() { this.getNumberOfArguments() = 3 }
 
     /**
      * Gets an HTTP status code that may be returned in this response.
      */
-    int getAStatusCode() { this.getElement(0) = trackStatusCode(result) }
+    int getAStatusCode() { this.getElement(0) = trackInt(result) }
   }
 
-  private DataFlow::LocalSourceNode trackRackResponse(TypeTracker t) {
+  private DataFlow::LocalSourceNode trackRackResponse(TypeTracker t, PotentialResponseNode n) {
     t.start() and
-    result instanceof ResponseNode
+    result = n
     or
-    exists(TypeTracker t2 | result = trackRackResponse(t2).track(t2, t))
+    exists(TypeTracker t2 | result = trackRackResponse(t2, n).track(t2, t))
   }
 
-  private DataFlow::Node trackRackResponse() {
-    trackRackResponse(TypeTracker::end()).flowsTo(result)
+  private DataFlow::Node trackRackResponse(PotentialResponseNode n) {
+    trackRackResponse(TypeTracker::end(), n).flowsTo(result)
+  }
+
+  /** A `DataFlow::Node` returned from a rack request. */
+  class ResponseNode extends PotentialResponseNode, Http::Server::HttpResponse::Range {
+    ResponseNode() { this = any(AppCandidate app).getResponse() }
+
+    override DataFlow::Node getBody() { result = this.getElement(2) }
+
+    // TODO
+    override DataFlow::Node getMimetypeOrContentTypeArg() { none() }
+
+    // TODO
+    override string getMimetypeDefault() { none() }
   }
 }
diff --git a/ruby/ql/test/library-tests/frameworks/rack/Rack.expected b/ruby/ql/test/library-tests/frameworks/rack/Rack.expected
index db76f4545b6..23fec9a8266 100644
--- a/ruby/ql/test/library-tests/frameworks/rack/Rack.expected
+++ b/ruby/ql/test/library-tests/frameworks/rack/Rack.expected
@@ -6,6 +6,7 @@ rackApps
 rackResponseStatusCodes
 | rack.rb:7:5:7:63 | call to [] | 200 |
 | rack.rb:7:5:7:63 | call to [] | 500 |
-| rack.rb:39:5:39:13 | call to [] | 1 |
+| rack.rb:18:5:18:27 | call to [] | <unknown> |
+| rack.rb:33:5:33:26 | call to [] | <unknown> |
 | rack.rb:56:7:56:22 | call to [] | 200 |
 | rack.rb:63:5:63:21 | call to [] | 400 |
diff --git a/ruby/ql/test/library-tests/frameworks/rack/Rack.ql b/ruby/ql/test/library-tests/frameworks/rack/Rack.ql
index 25c8303853d..6e18162a5e1 100644
--- a/ruby/ql/test/library-tests/frameworks/rack/Rack.ql
+++ b/ruby/ql/test/library-tests/frameworks/rack/Rack.ql
@@ -3,6 +3,8 @@ private import codeql.ruby.DataFlow
 
 query predicate rackApps(Rack::AppCandidate c, DataFlow::ParameterNode env) { env = c.getEnv() }
 
-query predicate rackResponseStatusCodes(Rack::ResponseNode resp, int status) {
-  status = resp.getAStatusCode()
+query predicate rackResponseStatusCodes(Rack::ResponseNode resp, string status) {
+  if exists(resp.getAStatusCode())
+  then status = resp.getAStatusCode().toString()
+  else status = "<unknown>"
 }