diff --git a/test/unit_test/static/CMakeLists.txt b/test/unit_test/static/CMakeLists.txt
index a15104c2..f0677c36 100644
--- a/test/unit_test/static/CMakeLists.txt
+++ b/test/unit_test/static/CMakeLists.txt
@@ -39,12 +39,12 @@ add_library(
     chrono_test.cpp
     concepts_test.cpp
     # custom_rep_test_min_expl.cpp
-    # custom_unit_test.cpp
     # dimension_op_test.cpp
     dimension_test.cpp
     # dimensions_concepts_test.cpp
     fixed_string_test.cpp
     # fps_test.cpp
+    fractional_exponent_quantity.cpp
     hep_test.cpp
     iec80000_test.cpp
     imperial_test.cpp
diff --git a/test/unit_test/static/fractional_exponent_quantity.cpp b/test/unit_test/static/fractional_exponent_quantity.cpp
new file mode 100644
index 00000000..d971efde
--- /dev/null
+++ b/test/unit_test/static/fractional_exponent_quantity.cpp
@@ -0,0 +1,50 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#include <mp-units/math.h>
+#include <mp-units/systems/isq/electromagnetism.h>
+#include <mp-units/systems/si/units.h>
+
+namespace {
+
+using namespace mp_units;
+
+QUANTITY_SPEC(power_spectral_density, pow<2>(isq::voltage) / isq::frequency);
+QUANTITY_SPEC(amplitude_spectral_density, sqrt(power_spectral_density));
+
+static_assert(implicitly_convertible(sqrt(power_spectral_density), amplitude_spectral_density));
+static_assert(implicitly_convertible(power_spectral_density, pow<2>(amplitude_spectral_density)));
+
+static_assert(sqrt(power_spectral_density).dimension == amplitude_spectral_density.dimension);
+static_assert(power_spectral_density.dimension == pow<2>(amplitude_spectral_density.dimension));
+
+static_assert(sqrt(square(si::volt) / si::hertz) == si::volt / sqrt(si::hertz));
+static_assert(square(si::volt) / si::hertz == pow<2>(si::volt / sqrt(si::hertz)));
+
+// TODO Should there be `pow()` and `sqrt()` for references as well? How to compare the results?
+
+static_assert(sqrt(16 * power_spectral_density[square(si::volt) / si::hertz]) ==
+              4 * amplitude_spectral_density[si::volt / sqrt(si::hertz)]);
+static_assert(16 * power_spectral_density[square(si::volt) / si::hertz] ==
+              pow<2>(4 * amplitude_spectral_density[si::volt / sqrt(si::hertz)]));
+
+}  // namespace