diff --git a/CHANGELOG.md b/CHANGELOG.md
index f334ed32..e09d135c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ Features
 - During CPS optimization allow inlining of operations on global variables that are mutated in other top-level functions.
 - Improved loop detection during CPS optimization phase.
 - Allow optimizing-out of basic `if` expressions of the form `(if (pred? ...) #t #f)` into `(pred? ...)`.
+- Perform slightly faster type checking for vector and bytevector access functions.
 
 Bug Fixes
 
diff --git a/runtime.c b/runtime.c
index c77568e8..5614aaf1 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2858,7 +2858,7 @@ object Cyc_bytevector_u8_ref(void *data, object bv, object k)
   int val;
 
   Cyc_check_bvec(data, bv);
-  Cyc_check_num(data, k);
+  Cyc_check_fixnum(data, k);
 
   buf = ((bytevector) bv)->data;
   idx = unbox_number(k);
@@ -2877,8 +2877,8 @@ object Cyc_bytevector_u8_set(void *data, object bv, object k, object b)
   int idx, len, val;
 
   Cyc_check_bvec(data, bv);
-  Cyc_check_num(data, k);
-  Cyc_check_num(data, b);
+  Cyc_check_fixnum(data, k);
+  Cyc_check_fixnum(data, b);
 
   buf = ((bytevector) bv)->data;
   idx = unbox_number(k);