diff --git a/tests/t1320-listproj.sh b/tests/t1320-listproj.sh
index 6037511..5f2f6fe 100755
--- a/tests/t1320-listproj.sh
+++ b/tests/t1320-listproj.sh
@@ -114,4 +114,9 @@ test_todo_session 'listproj from combined open + done tasks' <<'EOF'
 +prj01
 EOF
 
+test_todo_session 'listproj with GREP_OPTIONS disruption' <<'EOF'
+>>> GREP_OPTIONS=-n todo.sh listproj
++prj01
+EOF
+
 test_done
diff --git a/todo.sh b/todo.sh
index 7e75ceb..25078fb 100755
--- a/todo.sh
+++ b/todo.sh
@@ -467,6 +467,9 @@ OVR_TODOTXT_DEFAULT_ACTION="$TODOTXT_DEFAULT_ACTION"
 OVR_TODOTXT_SORT_COMMAND="$TODOTXT_SORT_COMMAND"
 OVR_TODOTXT_FINAL_FILTER="$TODOTXT_FINAL_FILTER"
 
+# Prevent GREP_OPTIONS from malforming grep's output
+GREP_OPTIONS=""
+
 # == PROCESS OPTIONS ==
 while getopts ":fhpcnNaAtTvVx+@Pd:" Option
 do