diff --git a/cde/programs/dtfile/Imakefile b/cde/programs/dtfile/Imakefile
index 112511239..279389c2f 100644
--- a/cde/programs/dtfile/Imakefile
+++ b/cde/programs/dtfile/Imakefile
@@ -24,6 +24,10 @@ SYS_LIBRARIES = DtClientSysLibs DtClientExtraLibs
 EXTRA_DEFINES = -D_TOOLTALK
 #endif
 
+#ifdef OpenBSDArchitecture
+EXTRA_DEFINES = -DFILE_MAP_OPTIMIZE
+#endif
+
 #if defined (SunArchitecture)
 EXTRA_CCOPTIONS = -xF
 #endif