diff --git a/src/Makefile.in b/src/Makefile.in
index a54c4be..7cec99f 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -90,7 +90,7 @@ cppcheck.out: $(HEADER_FILES) $(SOURCE_FILES)
 
 
 trexio.c trexio_f.f90 trexio.h: $(ORG_FILES)
-	./build_trexio.sh
+	cd ../tools && ./build_trexio.sh && cd ../src
 
 
 test_c: libtrexio.so test.c
diff --git a/tools/build_trexio.sh b/tools/build_trexio.sh
index 5c1b9ac..2eeee42 100755
--- a/tools/build_trexio.sh
+++ b/tools/build_trexio.sh
@@ -6,8 +6,13 @@ if [[ $(basename $PWD) != "tools" ]] ; then
   exit -1
 fi
 
+TREXIO_ROOT=$(dirname "${PWD}../")
+
+#   First define readonly global variables.
+readonly SRC=${TREXIO_ROOT}/src
+
 # Go to src directory
-cd ../src
+cd ${SRC}
 
 # We want the script to crash on the 1st error:
 set -e
@@ -80,5 +85,3 @@ source build.sh
 cp trexio* ../
 cd ..
 
-# Come back to the TREXIO root directory
-cd ..