diff --git a/src/main/java/org/kiwiproject/retry/StopStrategies.java b/src/main/java/org/kiwiproject/retry/StopStrategies.java
index cc650b9..acb1102 100644
--- a/src/main/java/org/kiwiproject/retry/StopStrategies.java
+++ b/src/main/java/org/kiwiproject/retry/StopStrategies.java
@@ -73,7 +73,7 @@ public static StopStrategy stopAfterDelay(long duration, @Nonnull TimeUnit timeU
     @Immutable
     private static final class NeverStopStrategy implements StopStrategy {
         @Override
-        public boolean shouldStop(Attempt failedAttempt) {
+        public boolean shouldStop(Attempt<?> failedAttempt) {
             return false;
         }
     }
@@ -88,7 +88,7 @@ private static final class StopAfterAttemptStrategy implements StopStrategy {
         }
 
         @Override
-        public boolean shouldStop(Attempt failedAttempt) {
+        public boolean shouldStop(Attempt<?> failedAttempt) {
             return failedAttempt.getAttemptNumber() >= maxAttemptNumber;
         }
     }
@@ -103,7 +103,7 @@ private static final class StopAfterDelayStrategy implements StopStrategy {
         }
 
         @Override
-        public boolean shouldStop(Attempt failedAttempt) {
+        public boolean shouldStop(Attempt<?> failedAttempt) {
             return failedAttempt.getDelaySinceFirstAttempt() >= maxDelay;
         }
     }
diff --git a/src/main/java/org/kiwiproject/retry/StopStrategy.java b/src/main/java/org/kiwiproject/retry/StopStrategy.java
index 34784a3..1fd981b 100644
--- a/src/main/java/org/kiwiproject/retry/StopStrategy.java
+++ b/src/main/java/org/kiwiproject/retry/StopStrategy.java
@@ -28,5 +28,5 @@ public interface StopStrategy {
      * @param failedAttempt the previous failed {@code Attempt}
      * @return <code>true</code> if the retryer must stop, <code>false</code> otherwise
      */
-    boolean shouldStop(Attempt failedAttempt);
+    boolean shouldStop(Attempt<?> failedAttempt);
 }
diff --git a/src/main/java/org/kiwiproject/retry/WaitStrategies.java b/src/main/java/org/kiwiproject/retry/WaitStrategies.java
index fa2c9d2..ee55cb3 100644
--- a/src/main/java/org/kiwiproject/retry/WaitStrategies.java
+++ b/src/main/java/org/kiwiproject/retry/WaitStrategies.java
@@ -240,7 +240,7 @@ private static final class FixedWaitStrategy implements WaitStrategy {
         }
 
         @Override
-        public long computeSleepTime(Attempt failedAttempt) {
+        public long computeSleepTime(Attempt<?> failedAttempt) {
             return sleepTime;
         }
     }
@@ -260,7 +260,7 @@ private static final class RandomWaitStrategy implements WaitStrategy {
         }
 
         @Override
-        public long computeSleepTime(Attempt failedAttempt) {
+        public long computeSleepTime(Attempt<?> failedAttempt) {
             long t = Math.abs(RANDOM.nextLong()) % (maximum - minimum);
             return t + minimum;
         }
@@ -279,7 +279,7 @@ private static final class IncrementingWaitStrategy implements WaitStrategy {
         }
 
         @Override
-        public long computeSleepTime(Attempt failedAttempt) {
+        public long computeSleepTime(Attempt<?> failedAttempt) {
             long result = initialSleepTime + (increment * (failedAttempt.getAttemptNumber() - 1));
             return result >= 0L ? result : 0L;
         }
@@ -300,7 +300,7 @@ private static final class ExponentialWaitStrategy implements WaitStrategy {
         }
 
         @Override
-        public long computeSleepTime(Attempt failedAttempt) {
+        public long computeSleepTime(Attempt<?> failedAttempt) {
             double exp = Math.pow(2, failedAttempt.getAttemptNumber());
             long result = Math.round(multiplier * exp);
             if (result > maximumWait) {
@@ -324,7 +324,7 @@ private static final class FibonacciWaitStrategy implements WaitStrategy {
         }
 
         @Override
-        public long computeSleepTime(Attempt failedAttempt) {
+        public long computeSleepTime(Attempt<?> failedAttempt) {
             long fib = fib(failedAttempt.getAttemptNumber());
             long result = multiplier * fib;
 
@@ -363,7 +363,7 @@ private static final class CompositeWaitStrategy implements WaitStrategy {
         }
 
         @Override
-        public long computeSleepTime(Attempt failedAttempt) {
+        public long computeSleepTime(Attempt<?> failedAttempt) {
             long waitTime = 0L;
             for (WaitStrategy waitStrategy : waitStrategies) {
                 waitTime += waitStrategy.computeSleepTime(failedAttempt);
@@ -384,7 +384,7 @@ private static final class ExceptionWaitStrategy<T extends Throwable> implements
 
         @SuppressWarnings({"unchecked"})
         @Override
-        public long computeSleepTime(Attempt lastAttempt) {
+        public long computeSleepTime(Attempt<?> lastAttempt) {
             if (lastAttempt.hasException()) {
                 Throwable cause = lastAttempt.getException();
                 if (exceptionClass.isAssignableFrom(cause.getClass())) {
diff --git a/src/main/java/org/kiwiproject/retry/WaitStrategy.java b/src/main/java/org/kiwiproject/retry/WaitStrategy.java
index 4b292ba..51cb74f 100644
--- a/src/main/java/org/kiwiproject/retry/WaitStrategy.java
+++ b/src/main/java/org/kiwiproject/retry/WaitStrategy.java
@@ -28,5 +28,5 @@ public interface WaitStrategy {
      * @param failedAttempt the previous failed {@code Attempt}
      * @return the sleep time before next attempt
      */
-    long computeSleepTime(Attempt failedAttempt);
+    long computeSleepTime(Attempt<?> failedAttempt);
 }