diff -r 591473851c95 -r 3d80d425543b src/buffer.c
--- a/src/buffer.c	Tue Jan 02 17:00:21 2018 +0100
+++ b/src/buffer.c	Sun Jan 21 10:13:21 2018 +0100
@@ -151,7 +151,10 @@
 
 size_t ucx_buffer_write(const void *ptr, size_t size, size_t nitems,
         UcxBuffer *buffer) {
-    size_t len = size * nitems;
+    size_t len;
+    if(ucx_szmul(size, nitems, &len)) {
+        return 0;
+    }
     size_t required = buffer->pos + len;
     if (buffer->pos > required) {
         return 0;
@@ -185,7 +188,10 @@
 
 size_t ucx_buffer_read(void *ptr, size_t size, size_t nitems,
         UcxBuffer *buffer) {
-    size_t len = size * nitems;
+    size_t len;
+    if(ucx_szmul(size, nitems, &len)) {
+        return 0;
+    }
     if (buffer->pos + len > buffer->size) {
         len = buffer->size - buffer->pos;
         if (size > 1) len -= len%size;