$OpenBSD$

Index: src/Common/CommonFunctions.cpp
--- src/Common/CommonFunctions.cpp.orig
+++ src/Common/CommonFunctions.cpp
@@ -54,7 +54,9 @@
 #include <Common/LuminanceOptions.h>
 
 #include <boost/algorithm/minmax_element.hpp>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 using namespace std;
 using namespace pfs;
