diff --git a/heed/src/database.rs b/heed/src/database.rs
index 026a2227..b46c33ff 100644
--- a/heed/src/database.rs
+++ b/heed/src/database.rs
@@ -1997,7 +1997,9 @@ impl<KC, DC, C> Database<KC, DC, C> {
     }
 
     /// Attempt to insert a key-value pair in this database, or if a value already exists for the
-    /// key, returns the previous value. The entry is written with no specific flag.
+    /// key, returns the previous value.
+    ///
+    /// The entry is always written with the [`NO_OVERWRITE`](PutFlags::NO_OVERWRITE) flag.
     ///
     /// ```
     /// # use heed::EnvOpenOptions;
@@ -2041,7 +2043,10 @@ impl<KC, DC, C> Database<KC, DC, C> {
     }
 
     /// Attempt to insert a key-value pair in this database, or if a value already exists for the
-    /// key, returns the previous value. The entry is written with the specified flags.
+    /// key, returns the previous value.
+    ///
+    /// The entry is written with the specified flags, in addition to
+    /// [`NO_OVERWRITE`](PutFlags::NO_OVERWRITE) which is always used.
     ///
     /// ```
     /// # use heed::EnvOpenOptions;
@@ -2113,7 +2118,8 @@ impl<KC, DC, C> Database<KC, DC, C> {
     /// Attempt to insert a key-value pair in this database, where the value can be directly
     /// written to disk, or if a value already exists for the key, returns the previous value.
     ///
-    /// The entry is written with no specific flags.
+    /// The entry is always written with the [`NO_OVERWRITE`](PutFlags::NO_OVERWRITE) and
+    /// [`MDB_RESERVE`](lmdb_master_sys::MDB_RESERVE) flags.
     ///
     /// ```
     /// # use heed::EnvOpenOptions;
@@ -2175,7 +2181,9 @@ impl<KC, DC, C> Database<KC, DC, C> {
     /// Attempt to insert a key-value pair in this database, where the value can be directly
     /// written to disk, or if a value already exists for the key, returns the previous value.
     ///
-    /// The entry is written with the specified flags.
+    /// The entry is written with the specified flags, in addition to
+    /// [`NO_OVERWRITE`](PutFlags::NO_OVERWRITE) and [`MDB_RESERVE`](lmdb_master_sys::MDB_RESERVE)
+    /// which are always used.
     ///
     /// ```
     /// # use heed::EnvOpenOptions;