diff --git a/src/cl-blas.lisp b/src/cl-blas.lisp
index dad1b8e..4e8da46 100644
--- a/src/cl-blas.lisp
+++ b/src/cl-blas.lisp
@@ -305,7 +305,7 @@
 (defblas gemm-serial ((A 2) (B 2) (C 2) (alpha 0) (beta 0))
   (loop with m fixnum = (array-dimension C 0)
         with n fixnum = (array-dimension C 1)
-        with r-block fixnum = (* (floor (array-dimension A 1) 8) 8)
+        with r-block fixnum = (* (floor (array-dimension A 1) stride) stride)
         with r fixnum = (array-dimension A 1)
         with Bt of-type (simple-array float 2) = (transpose B)
         for i fixnum from 0 below m