diff --git a/src/database.rs b/src/database.rs
index baf77eb..a5dff69 100644
--- a/src/database.rs
+++ b/src/database.rs
@@ -11,7 +11,7 @@ pub struct Database<'l> {
     _phantom: PhantomData<&'l raw::sqlite3>,
 }
 
-/// A callback executed for each row of the result of an SQL query.
+/// A callback triggered for each row of an executed SQL query.
 pub type ExecuteCallback<'l> = FnMut(Vec<(String, String)>) -> bool + 'l;
 
 impl<'l> Database<'l> {
diff --git a/src/lib.rs b/src/lib.rs
index 8433da4..d2f6cd9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -109,7 +109,7 @@ mod database;
 mod statement;
 
 pub use database::{Database, ExecuteCallback};
-pub use statement::{Statement, Binding};
+pub use statement::{Statement, Binding, Value};
 
 /// Open a database.
 #[inline]
diff --git a/src/statement.rs b/src/statement.rs
index f30358b..afd4d84 100644
--- a/src/statement.rs
+++ b/src/statement.rs
@@ -17,25 +17,30 @@ pub enum Binding<'l> {
     Text(usize, &'l str),
 }
 
-/// A value stored in a column.
+/// A value stored in a prepared statement.
 pub trait Value {
-    /// Read the value from a prepared statement at a specific position.
+    /// Read the value at a specific column.
     fn read(statement: &mut Statement, i: usize) -> Result<Self>;
 }
 
 impl<'l> Statement<'l> {
     /// Assign values to the placeholders.
+    ///
+    /// The leftmost parameter has an index of 1.
     pub fn bind(&mut self, bindings: &[Binding]) -> Result<()> {
         for binding in bindings.iter() {
             match *binding {
                 Binding::Float(i, value) => unsafe {
+                    debug_assert!(i > 0, "the indexation starts from 1");
                     success!(raw::sqlite3_bind_double(self.raw, i as c_int, value as c_double));
                 },
                 Binding::Integer(i, value) => unsafe {
+                    debug_assert!(i > 0, "the indexation starts from 1");
                     success!(raw::sqlite3_bind_int64(self.raw, i as c_int,
                                                      value as raw::sqlite3_int64));
                 },
                 Binding::Text(i, value) => unsafe {
+                    debug_assert!(i > 0, "the indexation starts from 1");
                     success!(raw::sqlite3_bind_text(self.raw, i as c_int, str_to_c_str!(value),
                                                     -1, None));
                 },