diff --git a/scripts/lcov.sh b/scripts/lcov.sh
index 0584a0aac7..9a0c58243f 100755
--- a/scripts/lcov.sh
+++ b/scripts/lcov.sh
@@ -39,13 +39,19 @@ in_mbedtls_build_dir () {
 lcov_library_report () {
     rm -rf Coverage
     mkdir Coverage Coverage/tmp
-    lcov --capture --initial --directory $library_dir -o Coverage/tmp/files.info
-    lcov --rc lcov_branch_coverage=1 --capture --directory $library_dir -o Coverage/tmp/tests.info
-    lcov --rc lcov_branch_coverage=1 --add-tracefile Coverage/tmp/files.info --add-tracefile Coverage/tmp/tests.info -o Coverage/tmp/all.info
-    lcov --rc lcov_branch_coverage=1 --remove Coverage/tmp/all.info -o Coverage/tmp/final.info '*.h'
-    gendesc tests/Descriptions.txt -o Coverage/tmp/descriptions
-    genhtml --title "$title" --description-file Coverage/tmp/descriptions --keep-descriptions --legend --branch-coverage -o Coverage Coverage/tmp/final.info
-    rm -f Coverage/tmp/*.info Coverage/tmp/descriptions
+    # Pass absolute paths as lcov output files. This works around a bug
+    # whereby lcov tries to create the output file in the root directory
+    # if it has emitted a warning. A fix was released in lcov 1.13 in 2016.
+    # Ubuntu 16.04 is affected, 18.04 and above are not.
+    # https://github.com/linux-test-project/lcov/commit/632c25a0d1f5e4d2f4fd5b28ce7c8b86d388c91f
+    COVTMP=$PWD/Coverage/tmp
+    lcov --capture --initial --directory $library_dir -o "$COVTMP/files.info"
+    lcov --rc lcov_branch_coverage=1 --capture --directory $library_dir -o "$COVTMP/tests.info"
+    lcov --rc lcov_branch_coverage=1 --add-tracefile "$COVTMP/files.info" --add-tracefile "$COVTMP/tests.info" -o "$COVTMP/all.info"
+    lcov --rc lcov_branch_coverage=1 --remove "$COVTMP/all.info" -o "$COVTMP/final.info" '*.h'
+    gendesc tests/Descriptions.txt -o "$COVTMP/descriptions"
+    genhtml --title "$title" --description-file "$COVTMP/descriptions" --keep-descriptions --legend --branch-coverage -o Coverage "$COVTMP/final.info"
+    rm -f "$COVTMP/"*.info "$COVTMP/descriptions"
     echo "Coverage report in: Coverage/index.html"
 }