1 files changed, 3 insertions, 3 deletions
diff --git a/src/main/java/au/id/zancanaro/javacheck/Generator.java b/src/main/java/au/id/zancanaro/javacheck/Generator.java
index 5a8fec3..24c23ca 100644
--- a/src/main/java/au/id/zancanaro/javacheck/Generator.java
+++ b/src/main/java/au/id/zancanaro/javacheck/Generator.java
@@ -111,7 +111,7 @@ public interface Generator<T> {
      * @param <R> The result of the transformation
      * @return A new generator resulting from mapping f over this
      */
-    default <R> Generator<R> map(Function<T, R> f) {
+    default <R> Generator<R> map(Function<? super T, ? extends R> f) {
         return (random, size) -> this.generate(random, size).map(f);
     }
 
@@ -127,7 +127,7 @@ public interface Generator<T> {
      * @return A new generator resulting from calling the provided action on the
      * result of this
      */
-    default <R> Generator<R> flatMap(Function<T, Generator<R>> action) {
+    default <R> Generator<R> flatMap(Function<? super T, ? extends Generator<R>> action) {
         return (random, size) -> ShrinkTree.join(
                 this.generate(random, size)
                         .map(action
@@ -148,7 +148,7 @@ public interface Generator<T> {
      * @return A new generator resulting from filtering this generator to only
      * terms which match the given predicate
      */
-    default Generator<T> suchThat(Predicate<T> predicate) {
+    default Generator<T> suchThat(Predicate<? super T> predicate) {
         return (random, size) -> {
             ShrinkTree<T> result = this.generate(random, size);
             if (predicate.test(result.getValue())) {