diff --git a/stress-iomix.c b/stress-iomix.c
index 204c71fdb..ff3b0c895 100644
--- a/stress-iomix.c
+++ b/stress-iomix.c
@@ -356,10 +356,16 @@ static void stress_iomix_rd_wr_mmap(const args_t *args, const int fd)
 					PROT_READ | PROT_WRITE, flags, fd, posn);
 		}
 		for (i = 0; i < SIZEOF_ARRAY(mmaps); i++) {
-			char buffer[page_size];
-
 			if (mmaps[i] != MAP_FAILED) {
-				memcpy(buffer, mmaps[i], page_size);
+				size_t j;
+				uint64_t sum = 0;
+				uint8_t *buffer =  (uint8_t *)mmaps[i];
+
+				/* Force page data to be read */
+				for (j = 0; j < page_size; j++)
+					sum += buffer[j];
+				uint64_put(sum);
+
 				stress_strnrnd(mmaps[i], page_size);
 				(void)shim_msync(mmaps[i], page_size,
 					(mwc32() & 1) ? MS_ASYNC : MS_SYNC);