diff --git a/test/accum.c b/test/accum.c
index 5a19efeebf5..9876998d9b4 100644
--- a/test/accum.c
+++ b/test/accum.c
@@ -2194,7 +2194,7 @@ test_swmr_write_big(bool newest_format)
         ZeroMemory(&pi, sizeof(pi));
 
         if (0 == CreateProcess(NULL, SWMR_READER, NULL, NULL, false, 0, NULL, NULL, &si, &pi)) {
-            printf("CreateProcess failed (%d).\n", GetLastError());
+            printf("CreateProcess failed (%lu).\n", GetLastError());
             FAIL_STACK_ERROR;
         }