diff --git a/spring-session/src/main/java/org/springframework/session/web/http/CookieHttpSessionStrategy.java b/spring-session/src/main/java/org/springframework/session/web/http/CookieHttpSessionStrategy.java
index 8bde751..8c3ebc1 100644
--- a/spring-session/src/main/java/org/springframework/session/web/http/CookieHttpSessionStrategy.java
+++ b/spring-session/src/main/java/org/springframework/session/web/http/CookieHttpSessionStrategy.java
@@ -238,7 +238,7 @@ public final class CookieHttpSessionStrategy implements MultiHttpSessionStrategy
 		if(sessionIds.isEmpty()) {
 			return "";
 		}
-		if(sessionIds.size() == 1) {
+		if(sessionIds.size() == 1 && sessionIds.keySet().contains(DEFAULT_ALIAS)) {
 			return sessionIds.values().iterator().next();
 		}
 
diff --git a/spring-session/src/test/java/org/springframework/session/web/http/CookieHttpSessionStrategyTests.java b/spring-session/src/test/java/org/springframework/session/web/http/CookieHttpSessionStrategyTests.java
index b7b7c3e..43942ef 100644
--- a/spring-session/src/test/java/org/springframework/session/web/http/CookieHttpSessionStrategyTests.java
+++ b/spring-session/src/test/java/org/springframework/session/web/http/CookieHttpSessionStrategyTests.java
@@ -107,6 +107,14 @@ public class CookieHttpSessionStrategyTests {
 		assertThat(getSessionId()).isEqualTo("0 " + existing.getId() + " new " + session.getId());
 	}
 
+	// gh-321
+	@Test
+	public void onNewSessionExplicitAlias() throws Exception {
+		request.setParameter(CookieHttpSessionStrategy.DEFAULT_SESSION_ALIAS_PARAM_NAME, "new");
+		strategy.onNewSession(session, request, response);
+		assertThat(getSessionId()).isEqualTo("new " + session.getId());
+	}
+
 	@Test
 	public void onNewSessionCookiePath() throws Exception {
 		request.setContextPath("/somethingunique");
@@ -149,8 +157,9 @@ public class CookieHttpSessionStrategyTests {
 	public void onDeleteSessionExistingSessionSameAlias() throws Exception {
 		Session existing = new MapSession();
 		setSessionCookie("0 " + existing.getId() + " new " + session.getId());
+		request.setParameter(CookieHttpSessionStrategy.DEFAULT_SESSION_ALIAS_PARAM_NAME, "new");
 		strategy.onInvalidateSession(request, response);
-		assertThat(getSessionId()).isEqualTo(session.getId());
+		assertThat(getSessionId()).isEqualTo(existing.getId());
 	}
 
 	@Test