diff --git a/src/lib.rs b/src/lib.rs
index 9a4e0169e8..d89647223c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -163,6 +163,7 @@ mod v256;
 mod v512;
 mod v64;
 
+/// 32-bit wide vector types
 mod v32 {
     use simd_llvm::*;
 
@@ -175,6 +176,7 @@ mod v32 {
     define_casts!((i8x4, i32x4, as_i32x4), (i16x2, i64x2, as_i64x4));
 }
 
+/// 16-bit wide vector types
 mod v16 {
     use simd_llvm::*;