diff --git a/kernel/x86_64/casum.c b/kernel/x86_64/casum.c
index a1bd76f33..60feec0ce 100644
--- a/kernel/x86_64/casum.c
+++ b/kernel/x86_64/casum.c
@@ -130,7 +130,7 @@ FLOAT CNAME(BLASLONG n, FLOAT *x, BLASLONG inc_x)
         mode = BLAS_DOUBLE | BLAS_COMPLEX;
 #endif
         blas_level1_thread_with_return_value(mode, n, 0, 0, dummy_alpha, x, inc_x, 
-                NULL, 0, result, 0, (void *)asum_thread_function, nthreads);
+                NULL, 0, result, 0, (int (*)(void))asum_thread_function, nthreads);
         ptr = (FLOAT *)result;
         for (i = 0; i < nthreads; i++) {
             sumf += (*ptr);