diff --git a/nodepool/driver/statemachine.py b/nodepool/driver/statemachine.py
index a3b61d04b..6b53e5aeb 100644
--- a/nodepool/driver/statemachine.py
+++ b/nodepool/driver/statemachine.py
@@ -871,9 +871,9 @@ class StateMachineProvider(Provider, QuotaSupport):
         known_uploads = set()
         uploads = self._zk.getProviderUploads(self.provider.name)
         for image in uploads.values():
-            for build in image.values():
+            for build_id, build in image.items():
                 for upload in build:
-                    known_uploads.add(upload.id)
+                    known_uploads.add(f'{build_id}-{upload.id}')
 
         newly_leaked_nodes = {}
         newly_leaked_uploads = {}
@@ -882,7 +882,13 @@ class StateMachineProvider(Provider, QuotaSupport):
             if pn != self.provider.name:
                 continue
             node_id = resource.metadata.get('nodepool_node_id')
+            build_id = resource.metadata.get('nodepool_build_id')
             upload_id = resource.metadata.get('nodepool_upload_id')
+            # Make a truly unique upload id
+            if upload_id:
+                build_upload_id = f'{build_id}-{upload_id}'
+            else:
+                build_upload_id = None
             if node_id and node_id not in known_nodes:
                 newly_leaked_nodes[node_id] = resource
                 if node_id in self.possibly_leaked_nodes:
@@ -898,9 +904,9 @@ class StateMachineProvider(Provider, QuotaSupport):
                     except Exception:
                         self.log.exception("Unable to delete leaked "
                                            f"resource for node {node_id}")
-            if upload_id and upload_id not in known_uploads:
-                newly_leaked_uploads[upload_id] = resource
-                if upload_id in self.possibly_leaked_uploads:
+            if build_upload_id and build_upload_id not in known_uploads:
+                newly_leaked_uploads[build_upload_id] = resource
+                if build_upload_id in self.possibly_leaked_uploads:
                     # We've seen this twice now, so it's not a race
                     # condition.
                     try:
@@ -911,8 +917,9 @@ class StateMachineProvider(Provider, QuotaSupport):
                                       resource.plural_metric_name))
                             self._statsd.incr(key, 1)
                     except Exception:
-                        self.log.exception("Unable to delete leaked "
-                                           f"resource for upload {upload_id}")
+                        self.log.exception(
+                            "Unable to delete leaked "
+                            f"resource for upload {build_upload_id}")
         self.possibly_leaked_nodes = newly_leaked_nodes
         self.possibly_leaked_uploads = newly_leaked_uploads
 
diff --git a/nodepool/tests/unit/test_driver_aws.py b/nodepool/tests/unit/test_driver_aws.py
index e7b0c852c..41c4d5878 100644
--- a/nodepool/tests/unit/test_driver_aws.py
+++ b/nodepool/tests/unit/test_driver_aws.py
@@ -1031,10 +1031,22 @@ class TestDriverAws(tests.DBTestCase):
 
     def test_aws_resource_cleanup_import_snapshot(self):
         # This tests the import_snapshot path
+
+        # Create a valid, non-leaked image to test id collisions, and
+        # that it is not deleted.
+        configfile = self.setup_config('aws/diskimage.yaml')
+        self.useBuilder(configfile)
+        current_image = self.waitForImage('ec2-us-west-2', 'fake-image')
+
+        # Assert the image exists
+        self.ec2.Image(current_image.external_id).state
+
         # Start by setting up leaked resources
+        # Use low numbers to intentionally collide with the current
+        # image to ensure we test the non-uniqueness of upload ids.
         image_tags = [
-            {'Key': 'nodepool_build_id', 'Value': '0000000042'},
-            {'Key': 'nodepool_upload_id', 'Value': '0000000042'},
+            {'Key': 'nodepool_build_id', 'Value': '0000000001'},
+            {'Key': 'nodepool_upload_id', 'Value': '0000000001'},
             {'Key': 'nodepool_provider_name', 'Value': 'ec2-us-west-2'}
         ]
 
@@ -1115,12 +1127,25 @@ class TestDriverAws(tests.DBTestCase):
                 # Probably not found
                 break
 
+        # Assert the non-leaked image still exists
+        self.ec2.Image(current_image.external_id).state
+
     def test_aws_resource_cleanup_import_image(self):
         # This tests the import_image path
+
+        # Create a valid, non-leaked image to test id collisions, and
+        # that it is not deleted.
+        configfile = self.setup_config('aws/diskimage.yaml')
+        self.useBuilder(configfile)
+        current_image = self.waitForImage('ec2-us-west-2', 'fake-image')
+
+        # Assert the image exists
+        self.ec2.Image(current_image.external_id).state
+
         # Start by setting up leaked resources
         image_tags = [
-            {'Key': 'nodepool_build_id', 'Value': '0000000042'},
-            {'Key': 'nodepool_upload_id', 'Value': '0000000042'},
+            {'Key': 'nodepool_build_id', 'Value': '0000000001'},
+            {'Key': 'nodepool_upload_id', 'Value': '0000000001'},
             {'Key': 'nodepool_provider_name', 'Value': 'ec2-us-west-2'}
         ]
 
@@ -1179,6 +1204,9 @@ class TestDriverAws(tests.DBTestCase):
                 # Probably not found
                 break
 
+        # Assert the non-leaked image still exists
+        self.ec2.Image(current_image.external_id).state
+
     def test_aws_get_import_image_task(self):
         # A unit test of the unusual error handling for missing tasks
         configfile = self.setup_config('aws/diskimage.yaml')