diff --git a/configure/CONFIG_SITE b/configure/CONFIG_SITE
index 1e64dd23a..894bb1ae2 100644
--- a/configure/CONFIG_SITE
+++ b/configure/CONFIG_SITE
@@ -161,7 +161,7 @@ USE_POSIX_THREAD_PRIORITY_SCHEDULING = YES
 
 # Site version number, if set will append '-' and this string to the
 #  EPICS version number string that is reported by many tools.
-EPICS_SITE_VERSION=$(shell $(PERL) -MPOSIX -e 'print strftime "%Y-%m-%d $(shell git describe --tags --dirty)", localtime')
+EPICS_SITE_VERSION=$(shell $(PERL) -MPOSIX -e 'print strftime "%Y-%m-%d_$(shell git describe --tags --dirty)", localtime')
 
 # For GNU compiler, use pipes rather than temporary files for
 #  communication between the various stages of compilation.