diff --git a/src/alphabets/dna.rs b/src/alphabets/dna.rs
index e3985c2ff..827af9627 100644
--- a/src/alphabets/dna.rs
+++ b/src/alphabets/dna.rs
@@ -62,6 +62,7 @@ lazy_static! {
 /// assert_eq!(dna::complement(89), 82); // Y → R
 /// assert_eq!(dna::complement(115), 115); // s → s
 /// ```
+#[inline]
 pub fn complement(a: u8) -> u8 {
     COMPLEMENT[a as usize]
 }
diff --git a/src/alphabets/rna.rs b/src/alphabets/rna.rs
index 9411d187b..8713b9a36 100644
--- a/src/alphabets/rna.rs
+++ b/src/alphabets/rna.rs
@@ -62,6 +62,7 @@ lazy_static! {
 /// assert_eq!(rna::complement(115), 115); // s → s
 /// assert_eq!(rna::complement(78), 78); // N → N
 /// ```
+#[inline]
 pub fn complement(a: u8) -> u8 {
     COMPLEMENT[a as usize]
 }