diff --git a/dsp/src/iir.rs b/dsp/src/iir.rs
index c6f2100..48c92e9 100644
--- a/dsp/src/iir.rs
+++ b/dsp/src/iir.rs
@@ -2,23 +2,13 @@ use core::ops::{Add, Mul, Neg};
 use serde::{Deserialize, Serialize};
 
 use core::f32;
+use super::abs;
 
 // These are implemented here because core::f32 doesn't have them (yet).
 // They are naive and don't handle inf/nan.
 // `compiler-intrinsics`/llvm should have better (robust, universal, and
 // faster) implementations.
 
-fn abs<T>(x: T) -> T
-where
-    T: PartialOrd + Default + Neg<Output = T>,
-{
-    if x >= T::default() {
-        x
-    } else {
-        -x
-    }
-}
-
 fn copysign<T>(x: T, y: T) -> T
 where
     T: PartialOrd + Default + Neg<Output = T>,
diff --git a/dsp/src/lib.rs b/dsp/src/lib.rs
index ef0c131..2fbd121 100644
--- a/dsp/src/lib.rs
+++ b/dsp/src/lib.rs
@@ -1,6 +1,8 @@
 #![cfg_attr(not(test), no_std)]
 #![cfg_attr(feature = "nightly", feature(asm, core_intrinsics))]
 
+use core::ops::Neg;
+
 pub type Complex<T> = (T, T);
 
 /// Round up half.
@@ -18,6 +20,17 @@ pub fn shift_round(x: i32, shift: usize) -> i32 {
     (x + (1 << (shift - 1))) >> shift
 }
 
+fn abs<T>(x: T) -> T
+where
+    T: PartialOrd + Default + Neg<Output = T>,
+{
+    if x >= T::default() {
+        x
+    } else {
+        -x
+    }
+}
+
 pub mod atan2;
 pub mod cossin;
 pub mod iir;