diff --git a/travis_custom/custom_build b/travis_custom/custom_build
index cfa041a7ddfdc2da1ff62597c3092ba8a85ac8a4..3c7d80ecdf63b723e0ce4ee8d06f2c18db0fdf9f 100755
--- a/travis_custom/custom_build
+++ b/travis_custom/custom_build
@@ -2,7 +2,7 @@
 set -e
 
 # Setup environment variables.
-export CMAKE_ADDITIONAL_OPTIONS=" ${CMAKE_ADDITIONAL_OPTIONS} -DBUILD_BENCHMARK=\"ON\" -DBUILD_UNIT_TESTS=\"ON\" -DCMAKE_CXX_FLAGS=-DBOOST_SYSTEM_NO_DEPRECATED"
+export CMAKE_ADDITIONAL_OPTIONS=" ${CMAKE_ADDITIONAL_OPTIONS} -DBUILD_BENCHMARK=\"ON\" -DBUILD_UNIT_TESTS=\"ON\" -DCMAKE_CXX_FLAGS=-DBOOST_SYSTEM_NO_DEPRECATED -DPYTHON_EXECUTABLE=$(which python)"
 if [[ ";${DO_INSTALL_DOC_EXCEPT_ON_BRANCH};" == *";${CI_BRANCH};"* ]]; then
   export CMAKE_ADDITIONAL_OPTIONS=" ${CMAKE_ADDITIONAL_OPTIONS} -DINSTALL_DOCUMENTATION=\"OFF\""
 else