diff --git a/cffu-core/src/main/java/io/foldright/cffu/CffuFactory.java b/cffu-core/src/main/java/io/foldright/cffu/CffuFactory.java
index 51f71ec5..aeaf3445 100644
--- a/cffu-core/src/main/java/io/foldright/cffu/CffuFactory.java
+++ b/cffu-core/src/main/java/io/foldright/cffu/CffuFactory.java
@@ -602,8 +602,9 @@ public Executor delayedExecutor(long delay, TimeUnit unit, Executor executor) {
      */
     @Contract(pure = true)
     @SafeVarargs
-    public final <T> Cffu<List<T>> cffuAllOf(Cffu<T>... cfs) {
-        return cffuAllOf(toCompletableFutureArray(cfs));
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    public final <T> Cffu<List<T>> cffuAllOf(Cffu<? extends T>... cfs) {
+        return cffuAllOf(toCompletableFutureArray((Cffu[]) cfs));
     }
 
     /**
@@ -622,7 +623,7 @@ public final <T> Cffu<List<T>> cffuAllOf(Cffu<T>... cfs) {
      */
     @Contract(pure = true)
     @SafeVarargs
-    public final <T> Cffu<List<T>> cffuAllOf(CompletableFuture<T>... cfs) {
+    public final <T> Cffu<List<T>> cffuAllOf(CompletableFuture<? extends T>... cfs) {
         return new0(CompletableFutureUtils.allOfWithResult(cfs));
     }
 
@@ -654,8 +655,9 @@ public <T> Cffu<List<T>> cffuAllOf() {
      */
     @Contract(pure = true)
     @SafeVarargs
-    public final <T> Cffu<List<T>> cffuAllOfFastFail(Cffu<T>... cfs) {
-        return cffuAllOfFastFail(toCompletableFutureArray(cfs));
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    public final <T> Cffu<List<T>> cffuAllOfFastFail(Cffu<? extends T>... cfs) {
+        return cffuAllOfFastFail(toCompletableFutureArray((Cffu[]) cfs));
     }
 
     /**
@@ -676,7 +678,7 @@ public final <T> Cffu<List<T>> cffuAllOfFastFail(Cffu<T>... cfs) {
      */
     @Contract(pure = true)
     @SafeVarargs
-    public final <T> Cffu<List<T>> cffuAllOfFastFail(CompletableFuture<T>... cfs) {
+    public final <T> Cffu<List<T>> cffuAllOfFastFail(CompletableFuture<? extends T>... cfs) {
         return new0(CompletableFutureUtils.allOfFastFailWithResult(cfs));
     }
 
@@ -705,8 +707,9 @@ public <T> Cffu<List<T>> cffuAllOfFastFail() {
      */
     @Contract(pure = true)
     @SafeVarargs
-    public final <T> Cffu<T> cffuAnyOf(Cffu<T>... cfs) {
-        return cffuAnyOf(toCompletableFutureArray(cfs));
+    @SuppressWarnings({"unchecked", "rawtypes"})
+    public final <T> Cffu<T> cffuAnyOf(Cffu<? extends T>... cfs) {
+        return cffuAnyOf(toCompletableFutureArray((Cffu[]) cfs));
     }
 
     /**
@@ -722,7 +725,7 @@ public final <T> Cffu<T> cffuAnyOf(Cffu<T>... cfs) {
      */
     @Contract(pure = true)
     @SafeVarargs
-    public final <T> Cffu<T> cffuAnyOf(CompletableFuture<T>... cfs) {
+    public final <T> Cffu<T> cffuAnyOf(CompletableFuture<? extends T>... cfs) {
         return new0(CompletableFutureUtils.anyOfWithType(cfs));
     }
 
@@ -752,8 +755,9 @@ public <T> Cffu<T> cffuAnyOf() {
      * @see #cffuAnyOf(Cffu[])
      */
     @SafeVarargs
-    public final <T> Cffu<T> cffuAnyOfSuccess(Cffu<T>... cfs) {
-        return cffuAnyOfSuccess(toCompletableFutureArray(cfs));
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    public final <T> Cffu<T> cffuAnyOfSuccess(Cffu<? extends T>... cfs) {
+        return cffuAnyOfSuccess(toCompletableFutureArray((Cffu[]) cfs));
     }
 
     /**
@@ -773,7 +777,7 @@ public final <T> Cffu<T> cffuAnyOfSuccess(Cffu<T>... cfs) {
      * @see #cffuAnyOf(Cffu[])
      */
     @SafeVarargs
-    public final <T> Cffu<T> cffuAnyOfSuccess(CompletableFuture<T>... cfs) {
+    public final <T> Cffu<T> cffuAnyOfSuccess(CompletableFuture<? extends T>... cfs) {
         return new0(CompletableFutureUtils.anyOfSuccessWithType(cfs));
     }
 
diff --git a/cffu-core/src/main/java/io/foldright/cffu/CompletableFutureUtils.java b/cffu-core/src/main/java/io/foldright/cffu/CompletableFutureUtils.java
index bf97ba37..421d29d4 100644
--- a/cffu-core/src/main/java/io/foldright/cffu/CompletableFutureUtils.java
+++ b/cffu-core/src/main/java/io/foldright/cffu/CompletableFutureUtils.java
@@ -50,7 +50,7 @@ public final class CompletableFutureUtils {
     @Contract(pure = true)
     @SafeVarargs
     @SuppressWarnings("unchecked")
-    public static <T> CompletableFuture<List<T>> allOfWithResult(CompletableFuture<T>... cfs) {
+    public static <T> CompletableFuture<List<T>> allOfWithResult(CompletableFuture<? extends T>... cfs) {
         requireCfsAndEleNonNull(cfs);
         final int size = cfs.length;
         if (size == 0) return CompletableFuture.completedFuture(arrayList());
@@ -121,7 +121,7 @@ public static CompletableFuture<Void> allOfFastFail(CompletableFuture<?>... cfs)
     @Contract(pure = true)
     @SafeVarargs
     @SuppressWarnings({"unchecked", "rawtypes"})
-    public static <T> CompletableFuture<List<T>> allOfFastFailWithResult(CompletableFuture<T>... cfs) {
+    public static <T> CompletableFuture<List<T>> allOfFastFailWithResult(CompletableFuture<? extends T>... cfs) {
         requireCfsAndEleNonNull(cfs);
         final int size = cfs.length;
         if (size == 0) return CompletableFuture.completedFuture(arrayList());
@@ -198,7 +198,7 @@ private static void fill(CompletableFuture[] cfs,
     @Contract(pure = true)
     @SafeVarargs
     @SuppressWarnings("unchecked")
-    public static <T> CompletableFuture<T> anyOfWithType(CompletableFuture<T>... cfs) {
+    public static <T> CompletableFuture<T> anyOfWithType(CompletableFuture<? extends T>... cfs) {
         return (CompletableFuture<T>) CompletableFuture.anyOf(cfs);
     }
 
@@ -256,7 +256,7 @@ public static CompletableFuture<Object> anyOfSuccess(CompletableFuture<?>... cfs
     @Contract(pure = true)
     @SafeVarargs
     @SuppressWarnings("unchecked")
-    public static <T> CompletableFuture<T> anyOfSuccessWithType(CompletableFuture<T>... cfs) {
+    public static <T> CompletableFuture<T> anyOfSuccessWithType(CompletableFuture<? extends T>... cfs) {
         return (CompletableFuture<T>) anyOfSuccess(cfs);
     }
 
diff --git a/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CompletableFutureExtensions.kt b/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CompletableFutureExtensions.kt
index 0c606add..05cfb044 100644
--- a/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CompletableFutureExtensions.kt
+++ b/cffu-kotlin/src/main/java/io/foldright/cffu/kotlin/CompletableFutureExtensions.kt
@@ -57,7 +57,7 @@ fun <T> Collection<CompletableFuture<T>>.allOfCompletableFuture(): CompletableFu
  * @see allOfCffu
  * @see allOfCompletableFutureVoid
  */
-fun <T> Array<CompletableFuture<T>>.allOfCompletableFuture(): CompletableFuture<List<T>> =
+fun <T> Array<out CompletableFuture<T>>.allOfCompletableFuture(): CompletableFuture<List<T>> =
     CompletableFutureUtils.allOfWithResult(*this)
 
 /**
@@ -137,7 +137,7 @@ fun <T> Collection<CompletableFuture<T>>.allOfFastFailCompletableFuture(): Compl
  * @see allOfFastFailCffu
  * @see allOfFastFailCompletableFutureVoid
  */
-fun <T> Array<CompletableFuture<T>>.allOfFastFailCompletableFuture(): CompletableFuture<List<T>> =
+fun <T> Array<out CompletableFuture<T>>.allOfFastFailCompletableFuture(): CompletableFuture<List<T>> =
     CompletableFutureUtils.allOfFastFailWithResult(*this)
 
 /**
@@ -217,7 +217,7 @@ fun <T> Collection<CompletableFuture<T>>.anyOfCompletableFuture(): CompletableFu
  * @see anyOfCffu
  * @see anyOfCompletableFutureAny
  */
-fun <T> Array<CompletableFuture<T>>.anyOfCompletableFuture(): CompletableFuture<T> =
+fun <T> Array<out CompletableFuture<T>>.anyOfCompletableFuture(): CompletableFuture<T> =
     CompletableFutureUtils.anyOfWithType(*this)
 
 /**
@@ -285,7 +285,7 @@ fun <T> Collection<CompletableFuture<T>>.anyOfSuccessCompletableFuture(): Comple
  * @see anyOfCompletableFuture
  * @see CompletableFutureUtils.anyOfSuccessWithType
  */
-fun <T> Array<CompletableFuture<T>>.anyOfSuccessCompletableFuture(): CompletableFuture<T> =
+fun <T> Array<out CompletableFuture<T>>.anyOfSuccessCompletableFuture(): CompletableFuture<T> =
     CompletableFutureUtils.anyOfSuccessWithType(*this)
 
 /**