diff --git a/port/cpl_vsil_unix_stdio_64.cpp b/port/cpl_vsil_unix_stdio_64.cpp
index d1619bb22bd0..6964b1e95083 100644
--- a/port/cpl_vsil_unix_stdio_64.cpp
+++ b/port/cpl_vsil_unix_stdio_64.cpp
@@ -145,7 +145,7 @@
 
 #ifndef BUILD_WITHOUT_64BIT_OFFSET
 // Ensure we have working 64 bit API
-static_assert(sizeof(VSI_FTELL64(nullptr)) == sizeof(vsi_l_offset),
+static_assert(sizeof(VSI_FTELL64(stdout)) == sizeof(vsi_l_offset),
               "File API does not seem to support 64-bit offset. "
               "If you still want to build GDAL without > 4GB file support, "
               "add the -DBUILD_WITHOUT_64BIT_OFFSET define");