diff --git a/src/db.c b/src/db.c
index 495300613..62ffda101 100644
--- a/src/db.c
+++ b/src/db.c
@@ -573,7 +573,18 @@ void signalModifiedKey(client *c, redisDb *db, robj *key) {
 }
 
 void signalFlushedDb(int dbid, int async) {
-    touchWatchedKeysOnFlush(dbid);
+    int startdb, enddb;
+    if (dbid == -1) {
+        startdb = 0;
+        enddb = server.dbnum-1;
+    } else {
+        startdb = enddb = dbid;
+    }
+
+    for (int j = startdb; j <= enddb; j++) {
+        touchAllWatchedKeysInDb(&server.db[j], NULL);
+    }
+
     trackingInvalidateKeysOnFlush(async);
 }
 
@@ -1331,9 +1342,14 @@ int dbSwapDatabases(long id1, long id2) {
      * However normally we only do this check for efficiency reasons
      * in dbAdd() when a list is created. So here we need to rescan
      * the list of clients blocked on lists and signal lists as ready
-     * if needed. */
+     * if needed.
+     *
+     * Also the swapdb should make transaction fail if there is any
+     * client watching keys */
     scanDatabaseForReadyLists(db1);
+    touchAllWatchedKeysInDb(db1, db2);
     scanDatabaseForReadyLists(db2);
+    touchAllWatchedKeysInDb(db2, db1);
     return C_OK;
 }
 
diff --git a/src/multi.c b/src/multi.c
index af0b0c612..d88c5f1b8 100644
--- a/src/multi.c
+++ b/src/multi.c
@@ -374,31 +374,36 @@ void touchWatchedKey(redisDb *db, robj *key) {
     }
 }
 
-/* On FLUSHDB or FLUSHALL all the watched keys that are present before the
- * flush but will be deleted as effect of the flushing operation should
- * be touched. "dbid" is the DB that's getting the flush. -1 if it is
- * a FLUSHALL operation (all the DBs flushed). */
-void touchWatchedKeysOnFlush(int dbid) {
-    listIter li1, li2;
+/* Set CLIENT_DIRTY_CAS to all clients of DB when DB is dirty.
+ * It may happen in the following situations:
+ * FLUSHDB, FLUSHALL, SWAPDB
+ *
+ * replaced_with: for SWAPDB, the WATCH should be invalidated if
+ * the key exists in either of them, and skipped only if it
+ * doesn't exist in both. */
+void touchAllWatchedKeysInDb(redisDb *emptied, redisDb *replaced_with) {
+    listIter li;
     listNode *ln;
+    dictEntry *de;
 
-    /* For every client, check all the waited keys */
-    listRewind(server.clients,&li1);
-    while((ln = listNext(&li1))) {
-        client *c = listNodeValue(ln);
-        listRewind(c->watched_keys,&li2);
-        while((ln = listNext(&li2))) {
-            watchedKey *wk = listNodeValue(ln);
+    if (dictSize(emptied->watched_keys) == 0) return;
 
-            /* For every watched key matching the specified DB, if the
-             * key exists, mark the client as dirty, as the key will be
-             * removed. */
-            if (dbid == -1 || wk->db->id == dbid) {
-                if (dictFind(wk->db->dict, wk->key->ptr) != NULL)
-                    c->flags |= CLIENT_DIRTY_CAS;
+    dictIterator *di = dictGetSafeIterator(emptied->watched_keys);
+    while((de = dictNext(di)) != NULL) {
+        robj *key = dictGetKey(de);
+        list *clients = dictGetVal(de);
+        if (!clients) continue;
+        listRewind(clients,&li);
+        while((ln = listNext(&li))) {
+            client *c = listNodeValue(ln);
+            if (dictFind(emptied->dict, key->ptr)) {
+                c->flags |= CLIENT_DIRTY_CAS;
+            } else if (replaced_with && dictFind(replaced_with->dict, key->ptr)) {
+                c->flags |= CLIENT_DIRTY_CAS;
             }
         }
     }
+    dictReleaseIterator(di);
 }
 
 void watchCommand(client *c) {
diff --git a/src/server.h b/src/server.h
index aaee5a35d..d79bf5b23 100644
--- a/src/server.h
+++ b/src/server.h
@@ -1864,7 +1864,7 @@ void initClientMultiState(client *c);
 void freeClientMultiState(client *c);
 void queueMultiCommand(client *c);
 void touchWatchedKey(redisDb *db, robj *key);
-void touchWatchedKeysOnFlush(int dbid);
+void touchAllWatchedKeysInDb(redisDb *emptied, redisDb *replaced_with);
 void discardTransaction(client *c);
 void flagTransaction(client *c);
 void execCommandAbort(client *c, sds error);
diff --git a/tests/unit/multi.tcl b/tests/unit/multi.tcl
index 25e417055..e22b6d43d 100644
--- a/tests/unit/multi.tcl
+++ b/tests/unit/multi.tcl
@@ -196,6 +196,29 @@ start_server {tags {"multi"}} {
         r exec
     } {PONG}
 
+    test {SWAPDB is able to touch the watched keys that exist} {
+        r flushall
+        r select 0
+        r set x 30
+        r watch x ;# make sure x (set to 30) doesn't change (SWAPDB will "delete" it)
+        r swapdb 0 1
+        r multi
+        r ping
+        r exec
+    } {}
+
+    test {SWAPDB is able to touch the watched keys that do not exist} {
+        r flushall
+        r select 1
+        r set x 30
+        r select 0
+        r watch x ;# make sure the key x (currently missing) doesn't change (SWAPDB will create it)
+        r swapdb 0 1
+        r multi
+        r ping
+        r exec
+    } {}
+
     test {WATCH is able to remember the DB a key belongs to} {
         r select 5
         r set x 30