diff --git a/include/boost/math/special_functions/spherical_harmonic.hpp b/include/boost/math/special_functions/spherical_harmonic.hpp
index 254626495..73513aeb6 100644
--- a/include/boost/math/special_functions/spherical_harmonic.hpp
+++ b/include/boost/math/special_functions/spherical_harmonic.hpp
@@ -119,7 +119,7 @@ std::complex<T> spherical_harmonic(unsigned n, int m, U theta, U phi, const Poli
    if(m&1)
    {
       // Check phase if theta is outside [0, PI]:
-      U mod = boost::math::tools::fmod_workaround(theta, T(2 * constants::pi<U>()));
+      U mod = boost::math::tools::fmod_workaround(theta, U(2 * constants::pi<U>()));
       if(mod < 0)
          mod += 2 * constants::pi<U>();
       if(mod > constants::pi<U>())