diff --git a/scrapy/core/downloader/__init__.py b/scrapy/core/downloader/__init__.py
index 1a1eb819e..3691df48a 100644
--- a/scrapy/core/downloader/__init__.py
+++ b/scrapy/core/downloader/__init__.py
@@ -102,13 +102,13 @@ class Downloader:
         key = self._get_slot_key(request, spider)
         if key not in self.slots:
             slot_settings = self.per_slot_settings.get(key, {})
-            conc = slot_settings.get(
-                'concurrency', (
-                    self.ip_concurrency if self.ip_concurrency else self.domain_concurrency
-                )
-            )
+            conc = (
+                self.ip_concurrency if self.ip_concurrency else self.domain_concurrency)
             conc, delay = _get_concurrency_delay(conc, spider, self.settings)
-            delay = slot_settings.get('delay', delay)
+            conc, delay = (
+                slot_settings.get('concurrency', conc),
+                slot_settings.get('delay', delay)
+            )
             randomize_delay = slot_settings.get('randomize_delay', self.randomize_delay)
             new_slot = Slot(conc, delay, randomize_delay)
             self.slots[key] = new_slot