diff --git a/deps.edn b/deps.edn
index 880c86e..18d0874 100644
--- a/deps.edn
+++ b/deps.edn
@@ -20,7 +20,8 @@
                       io.github.cognitect-labs/test-runner
                       {:git/tag "v0.5.0" :git/sha "48c3c67"}
                       ;; connection pooling
-                      com.zaxxer/HikariCP {:mvn/version "5.0.0"}
+                      ;; 5.0.0 requires JDK with class type 55:
+                      com.zaxxer/HikariCP {:mvn/version "3.4.2"}
                       com.mchange/c3p0 {:mvn/version "0.9.5.5"}
                       ;; JDBC drivers
                       ;; compatible with JDK8+: