diff --git a/Mage.Tests/src/test/java/org/mage/test/cards/abilities/keywords/ConvokeTest.java b/Mage.Tests/src/test/java/org/mage/test/cards/abilities/keywords/ConvokeTest.java
index 58b3ebb4da..ffccd56353 100644
--- a/Mage.Tests/src/test/java/org/mage/test/cards/abilities/keywords/ConvokeTest.java
+++ b/Mage.Tests/src/test/java/org/mage/test/cards/abilities/keywords/ConvokeTest.java
@@ -343,4 +343,28 @@ public class ConvokeTest extends CardTestPlayerBaseWithAIHelps {
 
         assertPermanentCount(playerA, "Hogaak, Arisen Necropolis", 1);
     }
+
+    @Test
+    public void test_Mana_MemoryOverflow() {
+        // possible bug: convoke mana calculation can overflow server's memory (too much mana options from too much permanents)
+        // https://github.com/magefree/mage/issues/6938
+
+        // Create X 1/1 white Soldier creature tokens with lifelink.
+        // Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature’s color.)
+        addCard(Zone.HAND, playerA, "March of the Multitudes", 1); // {X}{G}{W}{W}
+        addCard(Zone.BATTLEFIELD, playerA, "Grizzly Bears", 500);
+        addCard(Zone.BATTLEFIELD, playerA, "Forest", 1);
+        addCard(Zone.BATTLEFIELD, playerA, "Plains", 2);
+
+        castSpell(1, PhaseStep.PRECOMBAT_MAIN, playerA, "March of the Multitudes");
+        setChoice(playerA, "X=1");
+        addTarget(playerA, "Grizzly Bears"); // convoke pay
+
+        setStrictChooseMode(true);
+        setStopAt(1, PhaseStep.END_TURN);
+        execute();
+        assertAllCommandsUsed();
+
+        assertPermanentCount(playerA, "Soldier", 1);
+    }
 }
\ No newline at end of file
diff --git a/Mage/src/main/java/mage/abilities/mana/ManaOptions.java b/Mage/src/main/java/mage/abilities/mana/ManaOptions.java
index 68105ff096..fc8a7152cf 100644
--- a/Mage/src/main/java/mage/abilities/mana/ManaOptions.java
+++ b/Mage/src/main/java/mage/abilities/mana/ManaOptions.java
@@ -1,30 +1,27 @@
 package mage.abilities.mana;
 
-import java.util.ArrayList;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
 import mage.Mana;
 import mage.abilities.Ability;
-import mage.abilities.costs.Cost;
-import mage.abilities.costs.common.TapSourceCost;
 import mage.game.Game;
 import mage.game.events.GameEvent;
 import mage.game.events.ManaEvent;
 import mage.players.Player;
 import org.apache.log4j.Logger;
 
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
 /**
- *
  * @author BetaSteward_at_googlemail.com
- *
+ * <p>
  * this class is used to build a list of all possible mana combinations it can
  * be used to find all the ways to pay a mana cost or all the different mana
  * combinations available to a player
- *
+ * <p>
  * TODO: Conditional Mana is not supported yet. The mana adding removes the
  * condition of conditional mana
- *
  */
 public class ManaOptions extends ArrayList<Mana> {
 
@@ -87,6 +84,8 @@ public class ManaOptions extends ArrayList<Mana> {
                 }
             }
         }
+
+        forceManaDeduplication();
     }
 
     private void addManaVariation(List<Mana> netManas, ActivatedManaAbilityImpl ability, Game game) {
@@ -102,6 +101,8 @@ public class ManaOptions extends ArrayList<Mana> {
                 }
             }
         }
+
+        forceManaDeduplication();
     }
 
     private static List<List<Mana>> getSimulatedTriggeredManaFromPlayer(Game game, Ability ability) {
@@ -189,9 +190,9 @@ public class ManaOptions extends ArrayList<Mana> {
                                     if (startingMana.includesMana(manaCosts)) { // can pay the mana costs to use the ability
                                         if (!subtractCostAddMana(manaCosts, triggeredManaVariation, ability.getCosts().isEmpty(), startingMana)) {
                                             // the starting mana includes mana parts that the increased mana does not include, so add starting mana also as an option
-                                            add(prevMana);                                            
-                                        } 
-                                        wasUsable = true;                                         
+                                            add(prevMana);
+                                        }
+                                        wasUsable = true;
                                     } else {
                                         // mana costs can't be paid so keep starting mana
                                         add(prevMana);
@@ -251,10 +252,13 @@ public class ManaOptions extends ArrayList<Mana> {
                 }
             }
         }
+
         if (this.size() > 30 || replaces > 30) {
             logger.trace("ManaOptionsCosts " + this.size() + " Ign:" + replaces + " => " + this.toString());
             logger.trace("Abilities: " + abilities.toString());
         }
+        forceManaDeduplication();
+
         return wasUsable;
     }
 
@@ -302,6 +306,8 @@ public class ManaOptions extends ArrayList<Mana> {
                 }
             }
         }
+
+        forceManaDeduplication();
     }
 
     public void addMana(Mana addMana) {
@@ -311,6 +317,8 @@ public class ManaOptions extends ArrayList<Mana> {
         for (Mana mana : this) {
             mana.add(addMana);
         }
+
+        forceManaDeduplication();
     }
 
     public void addMana(ManaOptions options) {
@@ -335,6 +343,17 @@ public class ManaOptions extends ArrayList<Mana> {
                 }
             }
         }
+
+        forceManaDeduplication();
+    }
+
+    private void forceManaDeduplication() {
+        // memory overflow protection - force de-duplication on too much mana sources
+        // bug example: https://github.com/magefree/mage/issues/6938
+        // use it after new mana adding
+        if (this.size() > 1000) {
+            this.removeDuplicated();
+        }
     }
 
     public ManaOptions copy() {
@@ -408,14 +427,16 @@ public class ManaOptions extends ArrayList<Mana> {
             }
 
         }
+
+        forceManaDeduplication();
+
         return oldManaWasReplaced;
     }
 
     /**
-     * 
-     * @param number of generic mana 
+     * @param number        of generic mana
      * @param manaAvailable
-     * @return 
+     * @return
      */
     public static List<Mana> getPossiblePayCombinations(int number, Mana manaAvailable) {
         List<Mana> payCombinations = new ArrayList<>();