diff --git a/src/java/com/threerings/parlor/data/ParlorCodes.java b/src/java/com/threerings/parlor/data/ParlorCodes.java
index 477abe2f..e687706b 100644
--- a/src/java/com/threerings/parlor/data/ParlorCodes.java
+++ b/src/java/com/threerings/parlor/data/ParlorCodes.java
@@ -70,4 +70,8 @@ public interface ParlorCodes extends InvocationCodes
     /** An error code returned by the table services for a request to join a table that the
      * requester been banned from. */
     public static final String BANNED_FROM_TABLE = "m.banned_from_table";
+
+    /** An error code returned by the table services when a user requests to leave a table for
+     * which the game is already in progress. */
+    public static final String GAME_ALREADY_STARTED = "m.game_already_started";
 }
diff --git a/src/java/com/threerings/parlor/server/TableManager.java b/src/java/com/threerings/parlor/server/TableManager.java
index 03df94b9..f4aa2e39 100644
--- a/src/java/com/threerings/parlor/server/TableManager.java
+++ b/src/java/com/threerings/parlor/server/TableManager.java
@@ -245,6 +245,11 @@ public class TableManager
             throw new InvocationException(NO_SUCH_TABLE);
         }
 
+        // if the table is in play, the user is not allowed to leave (he must leave the game)
+        if (table.inPlay()) {
+            throw new InvocationException(GAME_ALREADY_STARTED);
+        }
+
         // request that the user be removed from the table
         if (!table.clearPlayer(leaver.getVisibleName())) {
             throw new InvocationException(NOT_AT_TABLE);