diff --git a/m4/db.m4 b/m4/db.m4
index c916c2b83..a9dd5ef2b 100644
--- a/m4/db.m4
+++ b/m4/db.m4
@@ -96,9 +96,9 @@ if test -z "$db_inc"; then
 fi
 
 dnl figure out which version of db we're using from the header file
-db_ver_maj=`grep DB_VERSION_MAJOR $db_incdir/db.h | awk '{print $3}'`
-db_ver_min=`grep DB_VERSION_MINOR $db_incdir/db.h | awk '{print $3}'`
-db_ver_pat=`grep DB_VERSION_PATCH $db_incdir/db.h | awk '{print $3}'`
+db_ver_maj=`gcc -E -fdirectives-only $db_incdir/db.h | grep DB_VERSION_MAJOR | awk '{print $3}'`
+db_ver_min=`gcc -E -fdirectives-only $db_incdir/db.h | grep DB_VERSION_MINOR | awk '{print $3}'`
+db_ver_pat=`gcc -E -fdirectives-only $db_incdir/db.h | grep DB_VERSION_PATCH | awk '{print $3}'`
 
 dnl Ensure that we have libdb at least 4.7, older versions aren't supported
 if test ${db_ver_maj} -lt 4; then