diff --git a/src/OneSmallerInt.zig b/src/OneSmallerInt.zig
new file mode 100644
index 0000000000000000000000000000000000000000..2e60a0f6afc4489641d42d068b3e573707d51139
--- /dev/null
+++ b/src/OneSmallerInt.zig
@@ -0,0 +1,40 @@
+const std = @import("std");
+const string = []const u8;
+const extras = @import("./lib.zig");
+
+pub fn OneSmallerInt(comptime T: type) type {
+    var info = @typeInfo(T);
+    info.Int.bits -= 1;
+    return @Type(info);
+}
+
+test {
+    try std.testing.expect(OneSmallerInt(u1) == u0);
+}
+test {
+    try std.testing.expect(OneSmallerInt(u2) == u1);
+}
+test {
+    try std.testing.expect(OneSmallerInt(u3) == u2);
+}
+test {
+    try std.testing.expect(OneSmallerInt(u4) == u3);
+}
+test {
+    try std.testing.expect(OneSmallerInt(u5) == u4);
+}
+test {
+    try std.testing.expect(OneSmallerInt(i1) == i0);
+}
+test {
+    try std.testing.expect(OneSmallerInt(i2) == i1);
+}
+test {
+    try std.testing.expect(OneSmallerInt(i3) == i2);
+}
+test {
+    try std.testing.expect(OneSmallerInt(i4) == i3);
+}
+test {
+    try std.testing.expect(OneSmallerInt(i5) == i4);
+}
diff --git a/src/lib.zig b/src/lib.zig
index 3f0ed08ed25aae1e4a309501f7af12559fa59279..94d181a47d0fd80e64d211fd29b3c59c045f6a05 100644
--- a/src/lib.zig
+++ b/src/lib.zig
@@ -93,3 +93,4 @@ pub usingnamespace @import("./rawInt.zig");
 pub usingnamespace @import("./expectSimilarType.zig");
 pub usingnamespace @import("./rawIntBytes.zig");
 pub usingnamespace @import("./globalOption.zig");
+pub usingnamespace @import("./OneSmallerInt.zig");