diff --git a/extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/DynamicallyAuthenticatedDataSource.java b/extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/DynamicallyAuthenticatedDataSource.java
index 1936d1e96..4c8e3c0f8 100644
--- a/extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/DynamicallyAuthenticatedDataSource.java
+++ b/extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/DynamicallyAuthenticatedDataSource.java
@@ -80,6 +80,13 @@ public class DynamicallyAuthenticatedDataSource extends PooledDataSource {
 
         });
 
+        // Force recalculation of expectedConnectionTypeCode. The
+        // PooledDataSource constructor accepting a single UnpooledDataSource
+        // will otherwise leave this value uninitialized, resulting in all
+        // connections failing to pass sanity checks and never being returned
+        // to the pool.
+        super.forceCloseAll();
+
     }
 
     @Override