diff --git a/AnkiDroid/src/main/java/com/ichi2/libanki/Collection.java b/AnkiDroid/src/main/java/com/ichi2/libanki/Collection.java
index f18b2dd2431a..c4f4438ff8b3 100644
--- a/AnkiDroid/src/main/java/com/ichi2/libanki/Collection.java
+++ b/AnkiDroid/src/main/java/com/ichi2/libanki/Collection.java
@@ -2124,4 +2124,17 @@ public Context getContext() {
         return mContext;
     }
 
+    /** Not in libAnki */
+
+    //This duplicates _loadScheduler (but returns the value and sets the report limit).
+    public Sched createScheduler(int reportLimit) {
+        int ver = schedVer();
+        if (ver == 1) {
+            mSched = new Sched(this);
+        } else if (ver == 2) {
+            mSched = new SchedV2(this);
+        }
+        mSched.setReportLimit(reportLimit);
+        return mSched;
+    }
 }
diff --git a/AnkiDroid/src/main/java/com/ichi2/libanki/Sched.java b/AnkiDroid/src/main/java/com/ichi2/libanki/Sched.java
index b08300c2013a..c088ebb1c002 100644
--- a/AnkiDroid/src/main/java/com/ichi2/libanki/Sched.java
+++ b/AnkiDroid/src/main/java/com/ichi2/libanki/Sched.java
@@ -2486,6 +2486,20 @@ public boolean leechActionSuspend(Card card) {
         }
     }
 
+    /** not in libAnki. Added due to #5666: inconsistent selected deck card counts on sync */
+    public int[] recalculateCounts() {
+        _resetLrnCount();
+        _resetNewCount();
+        _resetRevCount();
+        return new int[] { mNewCount, mLrnCount, mRevCount };
+    }
+
+    public void setReportLimit(int reportLimit) {
+        this.mReportLimit = reportLimit;
+    }
+
+    /** End #5666 */
+
 
     public void setContext(WeakReference<Activity> contextReference) {
         mContextReference = contextReference;
diff --git a/AnkiDroid/src/main/java/com/ichi2/libanki/SchedV2.java b/AnkiDroid/src/main/java/com/ichi2/libanki/SchedV2.java
index 060ed7acf7a6..392c10fd69e3 100644
--- a/AnkiDroid/src/main/java/com/ichi2/libanki/SchedV2.java
+++ b/AnkiDroid/src/main/java/com/ichi2/libanki/SchedV2.java
@@ -2744,4 +2744,19 @@ public void setContext(WeakReference<Activity> contextReference) {
         mContextReference = contextReference;
     }
 
+    /** not in libAnki. Added due to #5666: inconsistent selected deck card counts on sync */
+    @Override
+    public int[] recalculateCounts() {
+        _resetLrnCount();
+        _resetNewCount();
+        _resetRevCount();
+        return new int[] { mNewCount, mLrnCount, mRevCount };
+    }
+
+    @Override
+    public void setReportLimit(int reportLimit) {
+        this.mReportLimit = reportLimit;
+    }
+
+    /** End #5666 */
 }
diff --git a/AnkiDroid/src/main/java/com/ichi2/libanki/sync/Syncer.java b/AnkiDroid/src/main/java/com/ichi2/libanki/sync/Syncer.java
index f4195ceb9026..12c2171ab085 100644
--- a/AnkiDroid/src/main/java/com/ichi2/libanki/sync/Syncer.java
+++ b/AnkiDroid/src/main/java/com/ichi2/libanki/sync/Syncer.java
@@ -27,6 +27,7 @@
 import com.ichi2.async.Connection;
 import com.ichi2.libanki.Collection;
 import com.ichi2.libanki.Consts;
+import com.ichi2.libanki.Sched;
 import com.ichi2.libanki.Utils;
 
 import org.json.JSONArray;
@@ -57,6 +58,9 @@ public class Syncer {
     public static final int TYPE_STRING = 3;
     public static final int TYPE_BLOB = 4;
 
+    /** The libAnki value of `sched.mReportLimit` */
+    private static final int SYNC_SCHEDULER_REPORT_LIMIT = 1000;
+
     private Collection mCol;
     private HttpSyncer mServer;
     private long mRMod;
@@ -377,7 +381,11 @@ public JSONObject sanityCheck() {
             // return summary of deck
             JSONArray ja = new JSONArray();
             JSONArray sa = new JSONArray();
-            for (int c : mCol.getSched().counts()) {
+
+            //#5666 - not in libAnki
+            //We modified mReportLimit inside the scheduler, and this causes issues syncing dynamic decks.
+            Sched syncScheduler = mCol.createScheduler(SYNC_SCHEDULER_REPORT_LIMIT);
+            for (int c : syncScheduler.recalculateCounts()) {
                 sa.put(c);
             }
             ja.put(sa);