diff --git a/lib/galaxy/model/__init__.py b/lib/galaxy/model/__init__.py
index 9b0b2d63b89..b1b3e738b4c 100644
--- a/lib/galaxy/model/__init__.py
+++ b/lib/galaxy/model/__init__.py
@@ -3081,20 +3081,22 @@ class WorkflowInvocation( object, Dictifiable ):
     def to_dict( self, view='collection', value_mapper=None ):
         rval = super( WorkflowInvocation, self ).to_dict( view=view, value_mapper=value_mapper )
         if view == 'element':
-            steps = {}
+            steps = []
             for step in self.steps:
                 v = step.to_dict()
-                steps[str(v['order_index'])] = v
+                steps.append( v )
             rval['steps'] = steps
 
             inputs = {}
             for step in self.steps:
                 if step.workflow_step.type == 'tool':
                     for step_input in step.workflow_step.input_connections:
-                        if step_input.output_step.type == 'data_input':
+                        output_step_type = step_input.output_step.type
+                        if output_step_type in [ 'data_input', 'data_collection_input' ]:
+                            src = "hda" if output_step_type == 'data_input' else 'hdca'
                             for job_input in step.job.input_datasets:
                                 if job_input.name == step_input.input_name:
-                                    inputs[str(step_input.output_step.order_index)] = { "id": job_input.dataset_id, "src": "hda"}
+                                    inputs[str(step_input.output_step.order_index)] = { "id": job_input.dataset_id, "src": src }
             rval['inputs'] = inputs
         return rval
 
diff --git a/test/api/test_workflows.py b/test/api/test_workflows.py
index afeaab66b4c..e714f93688f 100644
--- a/test/api/test_workflows.py
+++ b/test/api/test_workflows.py
@@ -520,8 +520,8 @@ class WorkflowsApiTestCase( api.ApiTestCase ):
         usage_details = usage_details_response.json()
         # Assert some high-level things about the structure of data returned.
         self._assert_has_keys( usage_details, "inputs", "steps" )
-        for step in usage_details[ "steps" ].values():
-            self._assert_has_keys( step, "workflow_step_id", "order_index" )
+        for step in usage_details[ "steps" ]:
+            self._assert_has_keys( step, "workflow_step_id", "order_index", "id" )
 
     @skip_without_tool( "cat1" )
     def test_post_job_action( self ):