diff --git a/tests/compile-tests/fail/odd-capacity/Cargo.toml b/tests/compile-tests/fail/odd-capacity/Cargo.toml
new file mode 100644
index 0000000..48bf89f
--- /dev/null
+++ b/tests/compile-tests/fail/odd-capacity/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "odd-capacity"
+version = "0.1.0"
+edition = "2021"
+rust-version = "1.63.0"
+
+[workspace]
+
+[dependencies]
+hex = { package = "hex-conservative", path = "../../../../" }
diff --git a/tests/compile-tests/fail/odd-capacity/src/main.rs b/tests/compile-tests/fail/odd-capacity/src/main.rs
new file mode 100644
index 0000000..4624b6b
--- /dev/null
+++ b/tests/compile-tests/fail/odd-capacity/src/main.rs
@@ -0,0 +1,6 @@
+use hex::buf_encoder::BufEncoder;
+use hex::Case;
+
+// This should fail to compile because the capacity size is odd.
+// The only difference to `even-capacity` is the capacity size.
+fn main() { let _encoder = BufEncoder::<3>::new(Case::Lower); }
diff --git a/tests/compile-tests/pass/even-capacity/Cargo.toml b/tests/compile-tests/pass/even-capacity/Cargo.toml
new file mode 100644
index 0000000..d378dda
--- /dev/null
+++ b/tests/compile-tests/pass/even-capacity/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "even-capacity"
+version = "0.1.0"
+edition = "2021"
+rust-version = "1.63.0"
+
+[workspace]
+
+[dependencies]
+hex = { package = "hex-conservative", path = "../../../../" }
diff --git a/tests/compile-tests/pass/even-capacity/src/main.rs b/tests/compile-tests/pass/even-capacity/src/main.rs
new file mode 100644
index 0000000..f22133c
--- /dev/null
+++ b/tests/compile-tests/pass/even-capacity/src/main.rs
@@ -0,0 +1,5 @@
+use hex::buf_encoder::BufEncoder;
+use hex::Case;
+
+// This should compile, ensuring that the compile error in odd-capacity is from the odd capacity.
+fn main() { let _encoder = BufEncoder::<4>::new(Case::Lower); }