diff --git a/src/test-gradient-sample-nonsmooth.cc b/src/test-gradient-sample-nonsmooth.cc
index 63c8034fe35dd880bcde45e4b7796931a8740983..e684f204e7cf8d947fca66b65d98486853e0d81c 100644
--- a/src/test-gradient-sample-nonsmooth.cc
+++ b/src/test-gradient-sample-nonsmooth.cc
@@ -48,8 +48,8 @@ int main() {
 
     SmallVector numerical_descent;
     J.descentDirection(start, numerical_descent);
-    SmallVector analytic_descent = { -(7 / sqrt(5) - 1),
-                                     -(11.5 / sqrt(5) - 2) };
+    SmallVector analytic_descent = { -(7 / std::sqrt(5) - 1),
+                                     -(11.5 / std::sqrt(5) - 2) };
     assert(two_distance<dim>(analytic_descent, numerical_descent) < 1e-10);
 
     functionTester(J, start, 6);
@@ -61,8 +61,8 @@ int main() {
 
     SmallVector numerical_descent;
     J.descentDirection(start, numerical_descent);
-    SmallVector analytic_descent = { -(8 / sqrt(5) - 1),
-                                     -(13.5 / sqrt(5) - 2) };
+    SmallVector analytic_descent = { -(8 / std::sqrt(5) - 1),
+                                     -(13.5 / std::sqrt(5) - 2) };
     assert(two_distance<dim>(analytic_descent, numerical_descent) < 1e-10);
 
     functionTester(J, start, 6);
diff --git a/src/test-gradient-sample.cc b/src/test-gradient-sample.cc
index c7a8dc5ae5c6199c1345d82280d2cf15e38c8034..479273779081daa5c24438b33b1c3370e32c9592 100644
--- a/src/test-gradient-sample.cc
+++ b/src/test-gradient-sample.cc
@@ -34,8 +34,8 @@ int main() {
     = 17*(6, 9.5) - (1, 2) + 2/sqrt(5) (1, 2)
     = (102 - 1 + 2/sqrt(5), 161.5 - 2 + 4/sqrt(5))
   */
-  SmallVector analytic_descent = { -(102 - 1 + 2 / sqrt(5)),
-                                   -(161.5 - 2 + 4 / sqrt(5)) };
+  SmallVector analytic_descent = { -(102 - 1 + 2 / std::sqrt(5)),
+                                   -(161.5 - 2 + 4 / std::sqrt(5)) };
   SmallVector numerical_descent;
   J.descentDirection(SmallVector({ 17, 34 }), numerical_descent);
   assert(two_distance<dim>(analytic_descent, numerical_descent) < 1e-10);