diff --git a/forge-game/src/main/java/forge/game/GameActionUtil.java b/forge-game/src/main/java/forge/game/GameActionUtil.java
index 432477be2a36..eda847ec4f56 100644
--- a/forge-game/src/main/java/forge/game/GameActionUtil.java
+++ b/forge-game/src/main/java/forge/game/GameActionUtil.java
@@ -301,7 +301,15 @@ public static SpellAbility getGraveyardSpellByKeyword(KeywordInterface inst, Spe
         // there is a flashback cost (and not the cards cost)
         if (keyword.contains(":")) { // K:Flashback:Cost:ExtraParams:ExtraDescription
             final String[] k = keyword.split(":");
-            newSA = sa.copyWithManaCostReplaced(activator, new Cost(k[1], false));
+            
+            // Default to mana cost if no cost provided
+            final String costString = k[1];
+            if (costString.equals("")) {
+                newSA = sa.copy(activator);
+            } else {
+                newSA = sa.copyWithManaCostReplaced(activator, new Cost(k[1], false));
+            }
+
             String extraParams =  k.length > 2 ? k[2] : "";
             if (!extraParams.isEmpty()) {
                 for (Map.Entry<String, String> param : AbilityFactory.getMapParams(extraParams).entrySet()) {
diff --git a/forge-game/src/main/java/forge/game/card/CardFactoryUtil.java b/forge-game/src/main/java/forge/game/card/CardFactoryUtil.java
index 545242b952f6..b3965442ad9e 100644
--- a/forge-game/src/main/java/forge/game/card/CardFactoryUtil.java
+++ b/forge-game/src/main/java/forge/game/card/CardFactoryUtil.java
@@ -2223,7 +2223,15 @@ public static void addReplacementEffect(final KeywordInterface inst, final CardS
 
             if (keyword.contains(":")) { // K:Flashback:Cost:ExtraParams:ExtraDescription
                 final String[] k = keyword.split(":");
-                final Cost cost = new Cost(k[1], false);
+
+                // Default to mana cost if no cost provided
+                final String costString = k[1];
+                Cost cost;
+                if (costString.equals("")) {
+                    cost = new Cost(card.getManaCost(), false);
+                } else {
+                    cost = new Cost(k[1], false);
+                }
                 sb.append(cost.isOnlyManaCost() ? " " : "—").append(cost.toSimpleString());
                 sb.append(cost.isOnlyManaCost() ? "" : ".");