diff --git a/gdb/config/mips/irix3.mh b/gdb/config/mips/irix3.mh
index 0a7b7b417ac..311d697cb58 100644
--- a/gdb/config/mips/irix3.mh
+++ b/gdb/config/mips/irix3.mh
@@ -3,5 +3,4 @@ XDEPFILES=
 XM_FILE= xm-irix3.h
 NAT_FILE= nm-irix3.h
 NATDEPFILES= fork-child.o corelow.o infptrace.o inftarg.o mips-nat.o
-MUNCH_DEFINE=-B
 XM_CLIBS=-lbsd
diff --git a/gdb/config/mips/irix4.mh b/gdb/config/mips/irix4.mh
index 01d56745391..68511e6b9a4 100644
--- a/gdb/config/mips/irix4.mh
+++ b/gdb/config/mips/irix4.mh
@@ -3,7 +3,6 @@ XDEPFILES= ser-tcp.o
 XM_FILE= xm-irix4.h
 NAT_FILE= nm-irix4.h
 NATDEPFILES= fork-child.o procfs.o irix4-nat.o corelow.o
-MUNCH_DEFINE=-B
 XM_CLIBS=-lbsd -lsun
 # use cc in K&R mode, bump up some static compiler tables.
 CC = cc -cckr -Wf,-XNg1500 -Wf,-XNk1000 -Wf,-XNh1100