diff --git a/src/mg_schematic.cpp b/src/mg_schematic.cpp
index d203a7105..bb60cf5fd 100644
--- a/src/mg_schematic.cpp
+++ b/src/mg_schematic.cpp
@@ -57,7 +57,8 @@ void Schematic::updateContentIds()
 
 	flags |= SCHEM_CIDS_UPDATED;
 
-	for (size_t i = 0; i != size.X * size.Y * size.Z; i++)
+	size_t bufsize = size.X * size.Y * size.Z;
+	for (size_t i = 0; i != bufsize; i++)
 		schemdata[i].setContent(c_nodes[schemdata[i].getContent()]);
 }