diff --git a/maths.cpp b/maths.cpp
index 976827b5..3c2aef59 100644
--- a/maths.cpp
+++ b/maths.cpp
@@ -109,3 +109,28 @@ template uint8_t  round_pow2 (uint8_t);
 template uint16_t round_pow2 (uint16_t);
 template uint32_t round_pow2 (uint32_t);
 template uint64_t round_pow2 (uint64_t);
+
+
+template <typename T>
+int
+sign (T val) {
+    return val >= 0 ? 1 : -1;
+}
+
+
+template <>
+int
+sign (float val) {
+    return copysign (1.0, val);
+}
+
+
+template <>
+int
+sign (double val) {
+    return copysign (1.0, val);
+}
+
+
+template int sign (int);
+
diff --git a/maths.hpp b/maths.hpp
index cb439066..e2fd2835 100644
--- a/maths.hpp
+++ b/maths.hpp
@@ -145,9 +145,7 @@ max (const T &a , const T &b , const Args &...args )
     { return max ( b > a ? b : a, args...); }
 
 
-inline double sign (double x) { return x >= 0 ? 1.0 : -1.0; }
-inline float  sign (float  x) { return x >= 0 ? 1.0 : -1.0; }
-inline int    sign (int    x) { return x >= 0 ? 1   : -1  ; }
-
+template <typename T>
+int sign (T val);
 
 #endif // __MATHS_HPP