diff --git a/src/index/ivf_flat.rs b/src/index/ivf_flat.rs
index e710162..05e2993 100644
--- a/src/index/ivf_flat.rs
+++ b/src/index/ivf_flat.rs
@@ -5,7 +5,7 @@ use super::*;
 use crate::error::Result;
 use crate::faiss_try;
 use std::mem;
-use std::os::raw::{c_int, c_char};
+use std::os::raw::{c_char, c_int};
 use std::ptr;
 
 /// Alias for the native implementation of a flat index.
diff --git a/src/index/pretransform.rs b/src/index/pretransform.rs
index eaa6255..5e706f9 100644
--- a/src/index/pretransform.rs
+++ b/src/index/pretransform.rs
@@ -64,6 +64,17 @@ where
             })
         }
     }
+
+    pub fn prepend_transform<LT: NativeVectorTransform>(&mut self, ltrans: LT) -> Result<()> {
+        unsafe {
+            faiss_try(faiss_IndexPreTransform_prepend_transform(
+                self.inner,
+                ltrans.inner_ptr(),
+            ))?;
+
+            Ok(())
+        }
+    }
 }
 
 impl IndexImpl {