diff --git a/src/connection.rs b/src/connection.rs
index 080b01c..b8c64cd 100644
--- a/src/connection.rs
+++ b/src/connection.rs
@@ -17,7 +17,7 @@ impl<'l> Connection<'l> {
     pub fn open<T: AsRef<Path>>(path: T) -> Result<Connection<'l>> {
         let mut raw = 0 as *mut _;
         unsafe {
-            ok!(ffi::sqlite3_open_v2(path_to_c_str!(path.as_ref()), &mut raw,
+            ok!(ffi::sqlite3_open_v2(path_to_cstr!(path.as_ref()).as_ptr(), &mut raw,
                                      ffi::SQLITE_OPEN_CREATE | ffi::SQLITE_OPEN_READWRITE,
                                      0 as *const _));
         }
@@ -32,8 +32,8 @@ impl<'l> Connection<'l> {
     #[inline]
     pub fn execute(&self, sql: &str) -> Result<()> {
         unsafe {
-            ok!(self.raw, ffi::sqlite3_exec(self.raw, str_to_c_str!(sql), None, 0 as *mut _,
-                                            0 as *mut _));
+            ok!(self.raw, ffi::sqlite3_exec(self.raw, str_to_cstr!(sql).as_ptr(), None,
+                                            0 as *mut _, 0 as *mut _));
         }
         Ok(())
     }
@@ -49,7 +49,7 @@ impl<'l> Connection<'l> {
     {
         unsafe {
             let callback = Box::new(callback);
-            ok!(self.raw, ffi::sqlite3_exec(self.raw, str_to_c_str!(sql),
+            ok!(self.raw, ffi::sqlite3_exec(self.raw, str_to_cstr!(sql).as_ptr(),
                                             Some(process_callback::<F>),
                                             &*callback as *const F as *mut F as *mut _,
                                             0 as *mut _));
diff --git a/src/lib.rs b/src/lib.rs
index 41e6f8f..c7c7fee 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -37,38 +37,20 @@ macro_rules! raise(
 );
 
 macro_rules! error(
-    ($connection:expr, $code:expr) => (
-        match ::error::last($connection) {
-            Some(error) => return Err(error),
-            None => return Err(::Error::from(::ErrorKind::from($code as isize))),
-        }
-    );
+    ($connection:expr, $code:expr) => (match ::error::last($connection) {
+        Some(error) => return Err(error),
+        None => return Err(::Error::from(::ErrorKind::from($code as isize))),
+    });
 );
 
 macro_rules! ok(
-    ($connection:expr, $result:expr) => (
-        match $result {
-            ::ffi::SQLITE_OK => {},
-            code => error!($connection, code),
-        }
-    );
-    ($result:expr) => (
-        match $result {
-            ::ffi::SQLITE_OK => {},
-            code => return Err(::Error::from(::ErrorKind::from(code as isize))),
-        }
-    );
-);
-
-macro_rules! path_to_c_str(
-    ($path:expr) => ({
-        match $path.to_str() {
-            Some(path) => match ::std::ffi::CString::new(path) {
-                Ok(string) => string.as_ptr(),
-                Err(_) => raise!("failed to process a path"),
-            },
-            None => raise!("failed to process a path"),
-        }
+    ($connection:expr, $result:expr) => (match $result {
+        ::ffi::SQLITE_OK => {},
+        code => error!($connection, code),
+    });
+    ($result:expr) => (match $result {
+        ::ffi::SQLITE_OK => {},
+        code => return Err(::Error::from(::ErrorKind::from(code as isize))),
     });
 );
 
@@ -83,13 +65,21 @@ macro_rules! c_str_to_string(
     );
 );
 
-macro_rules! str_to_c_str(
-    ($string:expr) => (
-        match ::std::ffi::CString::new($string) {
-            Ok(string) => string.as_ptr(),
-            Err(_) => raise!("failed to process a string"),
-        }
-    );
+macro_rules! path_to_cstr(
+    ($path:expr) => (match $path.to_str() {
+        Some(path) => match ::std::ffi::CString::new(path) {
+            Ok(string) => string,
+            _ => raise!("failed to process a path"),
+        },
+        _ => raise!("failed to process a path"),
+    });
+);
+
+macro_rules! str_to_cstr(
+    ($string:expr) => (match ::std::ffi::CString::new($string) {
+        Ok(string) => string,
+        _ => raise!("failed to process a string"),
+    });
 );
 
 mod connection;
diff --git a/src/statement.rs b/src/statement.rs
index 88d55d5..14076b6 100644
--- a/src/statement.rs
+++ b/src/statement.rs
@@ -109,7 +109,7 @@ impl<'l> Parameter for &'l str {
         debug_assert!(i > 0, "the indexing starts from 1");
         unsafe {
             ok!(statement.raw.1, ffi::sqlite3_bind_text(statement.raw.0, i as c_int,
-                                                        str_to_c_str!(*self), -1, None));
+                                                        str_to_cstr!(*self).as_ptr(), -1, None));
         }
         Ok(())
     }
@@ -146,7 +146,8 @@ impl Value for String {
 pub fn new<'l>(raw1: *mut ffi::sqlite3, sql: &str) -> Result<Statement<'l>> {
     let mut raw0 = 0 as *mut _;
     unsafe {
-        ok!(raw1, ffi::sqlite3_prepare_v2(raw1, str_to_c_str!(sql), -1, &mut raw0, 0 as *mut _));
+        ok!(raw1, ffi::sqlite3_prepare_v2(raw1, str_to_cstr!(sql).as_ptr(), -1, &mut raw0,
+                                          0 as *mut _));
     }
     Ok(Statement { raw: (raw0, raw1), phantom: PhantomData })
 }