diff --git a/internal/util-interface/src/main/java/xsbti/F1.java b/internal/util-interface/src/main/java/xsbti/F1.java
new file mode 100644
index 000000000..8797e9196
--- /dev/null
+++ b/internal/util-interface/src/main/java/xsbti/F1.java
@@ -0,0 +1,6 @@
+package xsbti;
+
+public interface F1<A1, R>
+{
+  R apply(A1 a1);
+}