diff --git a/sprout/complex/udl.hpp b/sprout/complex/udl.hpp
index f9b05704..da73a555 100644
--- a/sprout/complex/udl.hpp
+++ b/sprout/complex/udl.hpp
@@ -18,15 +18,15 @@ namespace sprout {
 			}
 
 			//
-			// _if
-			// _iF
+			// _i_f
+			// _i_F
 			//
 			inline SPROUT_CONSTEXPR sprout::complex<float>
-			operator"" _if(long double x) {
+			operator"" _i_f(long double x) {
 				return sprout::complex<float>(0, x);
 			}
 			inline SPROUT_CONSTEXPR sprout::complex<float>
-			operator"" _iF(long double x) {
+			operator"" _i_F(long double x) {
 				return sprout::complex<float>(0, x);
 			}
 
@@ -45,15 +45,15 @@ namespace sprout {
 		}	// namespace complex
 
 		using sprout::udl::complex::operator"" _i;
-		using sprout::udl::complex::operator"" _if;
-		using sprout::udl::complex::operator"" _iF;
+		using sprout::udl::complex::operator"" _i_f;
+		using sprout::udl::complex::operator"" _i_F;
 		using sprout::udl::complex::operator"" _il;
 		using sprout::udl::complex::operator"" _iL;
 	}	// namespace udl
 
 	using sprout::udl::complex::operator"" _i;
-	using sprout::udl::complex::operator"" _if;
-	using sprout::udl::complex::operator"" _iF;
+	using sprout::udl::complex::operator"" _i_f;
+	using sprout::udl::complex::operator"" _i_F;
 	using sprout::udl::complex::operator"" _il;
 	using sprout::udl::complex::operator"" _iL;
 }	// namespace sprout