diff --git a/configure/os/CONFIG.Common.RTEMS b/configure/os/CONFIG.Common.RTEMS
index 30b601969..73fe9f498 100644
--- a/configure/os/CONFIG.Common.RTEMS
+++ b/configure/os/CONFIG.Common.RTEMS
@@ -62,7 +62,7 @@ OS_CLASS = RTEMS
 
 #--------------------------------------------------
 # Operating system flags
-OP_SYS_CPPFLAGS = -Dfopen=rtems_fopen -Dmain=rtems_main -DIOCSH_USE_READLINE
+OP_SYS_CPPFLAGS = -Dfopen=rtems_fopen -Dmain=rtems_main
 OP_SYS_LDLIBS = -lreadline -lcurses
 OP_SYS_LDFLAGS = $(CPU_CFLAGS) -u Init -lCom \
                  $(PROJECT_RELEASE)/lib/no-dpmem.rel \
diff --git a/configure/os/CONFIG.linux-x86.linux-x86 b/configure/os/CONFIG.linux-x86.linux-x86
index 8a6a4ebb6..453e5a6eb 100644
--- a/configure/os/CONFIG.linux-x86.linux-x86
+++ b/configure/os/CONFIG.linux-x86.linux-x86
@@ -31,8 +31,6 @@ RANLIB = ranlib -t
 
 # -D_BSD_SOURCE for gethostname() in unistd.h as needed by cacChannelIO.cpp.
 ARCH_DEP_CPPFLAGS += -D_BSD_SOURCE
-# IOCSH_USE_READLINE needed by iocsh/ioccrf.c
-ARCH_DEP_CPPFLAGS += -DIOCSH_USE_READLINE
 ARCH_DEP_CPPFLAGS += -D_X86_ -Dlinux
 
 ARCH_DEP_LDFLAGS =