diff -r 9db71925eaa8 -r 4044131874f9 test/buffer_tests.c
--- a/test/buffer_tests.c	Fri Nov 18 15:33:58 2016 +0100
+++ b/test/buffer_tests.c	Fri Dec 16 23:22:18 2016 +0100
@@ -27,6 +27,7 @@
  */
 
 #include "buffer_tests.h"
+#include <stdint.h>
 
 UCX_TEST(test_ucx_buffer_new) {
     UcxBuffer *b = ucx_buffer_new(NULL, 16, UCX_BUFFER_AUTOEXTEND);
@@ -97,8 +98,12 @@
             "failed seek shall leave pos unchanged");
     
     b->pos = 0;
-    b->size = sizemax / 2 + 32;
-    off_t bigoff = sizemax / 2 - 16;
+    b->size = (sizemax >> 1) + 32;
+    
+    // we don't want to risk overflows in implicit constant casts
+    const size_t bigoff_comp = (sizemax >> 1) - 16;
+    off_t bigoff = (off_t)bigoff_comp;
+    
     r = ucx_buffer_seek(b, -bigoff, SEEK_CUR);
     UCX_TEST_ASSERT(r != 0, "seek cur underflow");
     UCX_TEST_ASSERT(b->pos == 0,