diff --git a/plan-refine b/plan-refine
index 5aa678b..e155d4f 100755
--- a/plan-refine
+++ b/plan-refine
@@ -36,7 +36,7 @@ set_frontmatter() {
         mv "$tmp" "$file"; return
     fi
     if grep -q "^${key}:" "$file"; then
-        sed -i '' "s|^${key}:.*|${key}: ${value}|" "$file"
+        sed "s|^${key}:.*|${key}: ${value}|" "$file" > "${file}.tmp" && mv "${file}.tmp" "$file"
     else
         awk -v key="$key" -v val="$value" '
             BEGIN { count=0; inserted=0 }