diff --git a/config/database.yml b/config/database.yml
index 34acf2f19..7216e44dd 100644
--- a/config/database.yml
+++ b/config/database.yml
@@ -1,6 +1,9 @@
 default: &default
   adapter: postgresql
-  pool: <%= ENV["DB_POOL"] || ENV['MAX_THREADS'] || 5 %>
+  # The db pool must contain at least one more connection than the number of threads.
+  # Each thread uses its own connection, and we need an additional connection used
+  # by the ActivityLogAudienceHelper
+  pool: <%= ENV["DB_POOL"] || ENV.fetch('MAX_THREADS', 5).to_i + 1 %>
   timeout: 5000
   connect_timeout: 15
   encoding: unicode