diff --git a/config/ChangeLog b/config/ChangeLog
index 6f27566974d..ab3a773049d 100644
--- a/config/ChangeLog
+++ b/config/ChangeLog
@@ -1,3 +1,9 @@
+2014-11-17  Bob Dunlop  <bob.dunlop@xyzzy.org.uk>
+
+	* mt-ospace (CFLAGS_FOR_TARGET): Append -g -Os rather than
+	overwriting.
+	(CXXFLAGS_FOR_TARGET): Similarly.
+
 2014-11-17  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR bootstrap/63888
diff --git a/config/mt-ospace b/config/mt-ospace
index 7f091041d8a..ce29ff4315d 100644
--- a/config/mt-ospace
+++ b/config/mt-ospace
@@ -1,3 +1,3 @@
 # Build libraries optimizing for space, not speed.
- CFLAGS_FOR_TARGET = -g -Os
- CXXFLAGS_FOR_TARGET = -g -Os
+ CFLAGS_FOR_TARGET += -g -Os
+ CXXFLAGS_FOR_TARGET += -g -Os