diff --git a/gdb/config/decstation.mh b/gdb/config/decstation.mh
index 28fcc1eb855..35b945d8a98 100644
--- a/gdb/config/decstation.mh
+++ b/gdb/config/decstation.mh
@@ -1,3 +1,5 @@
 # Host: Little-endian MIPS machine such as DECstation.
 XDEPFILES= infptrace.o mips-xdep.o coredep.o
 XM_FILE= xm-mips.h
+# Might need to uncomment this for old versions of Ultrix.
+XM_CFLAGS= -DHAVE_STRSTR