diff --git a/crates/resetprop/src/info.rs b/crates/resetprop/src/info.rs
index d66e2db..635ddf7 100644
--- a/crates/resetprop/src/info.rs
+++ b/crates/resetprop/src/info.rs
@@ -368,6 +368,18 @@ impl<'a> PropInfo<'a> {
             return Err(Error::ValueTooLong { len: value.len() });
         }
 
+        let old_len = {
+            let mut len = 0usize;
+            let max = self.area.len() - abs;
+            unsafe {
+                let ptr = self.area.base().add(abs);
+                while len < max && *ptr.add(len) != 0 {
+                    len += 1;
+                }
+            }
+            len
+        };
+
         unsafe {
             let ptr = self.area.base().add(abs);
             std::ptr::copy_nonoverlapping(value.as_ptr(), ptr, value.len());
@@ -378,6 +390,10 @@ impl<'a> PropInfo<'a> {
         std::sync::atomic::fence(Ordering::Release);
         self.serial_atomic().store(new_serial, Ordering::Release);
 
+        if value.len() < old_len {
+            self.area.compact()?;
+        }
+
         Ok(())
     }
 
diff --git a/crates/resetprop/src/mock.rs b/crates/resetprop/src/mock.rs
index 0f930e4..b1c84fe 100644
--- a/crates/resetprop/src/mock.rs
+++ b/crates/resetprop/src/mock.rs
@@ -556,6 +556,29 @@ mod tests {
         assert_eq!(area.arena_stats().bytes_used, before);
     }
 
+    #[test]
+    fn set_quiet_shrinking_long_value_compacts_arena() {
+        let mock = MockArea::new();
+        let area = mock.open();
+
+        let old = "a".repeat(92);
+        let new = "b".repeat(86);
+        area.set("ro.build.fingerprint", &old).unwrap();
+        let before = area.arena_stats().bytes_used;
+
+        area.set_quiet("ro.build.fingerprint", &new).unwrap();
+
+        assert_eq!(area.get("ro.build.fingerprint").unwrap(), new);
+        assert!(
+            area.arena_stats().bytes_used < before,
+            "shrinking a long value should reclaim its trailing allocation gap"
+        );
+        assert!(
+            !area.compact().unwrap(),
+            "quiet long-value shrink should leave no hole to compact"
+        );
+    }
+
     #[test]
     fn hexpatch_duplicate_length_segments() {
         let mock = MockArea::new();