diff --git a/v-hacd.spec b/v-hacd.spec
index cd7af8c..1b8cb13 100644
--- a/v-hacd.spec
+++ b/v-hacd.spec
@@ -5,6 +5,8 @@ Version:        4.1.0
 Release:        %autorelease
 Summary:        Decomposes a 3D surface into a set of “near” convex parts
 
+%undefine __cmake_in_source_build
+
 # The entire source is BSD-3-Clause, except:
 #   - app/wavefront.{h,cpp} are MIT
 License:        BSD-3-Clause AND MIT