diff --git a/libs/libc/Makefile b/libs/libc/Makefile
index 2068f663b7..56a677b97d 100644
--- a/libs/libc/Makefile
+++ b/libs/libc/Makefile
@@ -35,12 +35,6 @@
 
 -include $(TOPDIR)/Make.defs
 
-# CFLAGS
-
-ifneq ($(CONFIG_BUILD_FLAT),y)
-  KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
-endif
-
 # Sources and paths
 
 ASRCS =
diff --git a/libs/libnx/Makefile b/libs/libnx/Makefile
index ac7268fc8a..d9948fa295 100644
--- a/libs/libnx/Makefile
+++ b/libs/libnx/Makefile
@@ -35,12 +35,6 @@
 
 -include $(TOPDIR)/Make.defs
 
-# CFLAGS
-
-ifneq ($(CONFIG_BUILD_FLAT),y)
-  KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
-endif
-
 # Sources and paths
 
 ASRCS =
diff --git a/mm/Makefile b/mm/Makefile
index 32fd3f4ca4..e5865b00db 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -38,12 +38,6 @@
 # REVISIT: Backslash causes problems in $(COBJS) target
 DELIM := $(strip /)
 
-# CFLAGS
-
-ifneq ($(CONFIG_BUILD_FLAT),y)
-  KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
-endif
-
 # Sources and paths
 
 ASRCS  =
diff --git a/tools/Config.mk b/tools/Config.mk
index 764e2bae29..f96c40e6e3 100644
--- a/tools/Config.mk
+++ b/tools/Config.mk
@@ -60,6 +60,11 @@ CONFIG_ARCH_BOARD := $(patsubst "%",%,$(strip $(CONFIG_ARCH_BOARD)))
 OBJEXT ?= .o
 LIBEXT ?= .a
 
+# This define is passed as EXTRAFLAGS for kernel-mode builds.  It is also passed
+# during PASS1 (but not PASS2) context and depend targets.
+
+KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
+
 # DELIM - Path segment delimiter character
 #
 # Depends on this settings defined in board-specific defconfig file installed
diff --git a/tools/Makefile.unix b/tools/Makefile.unix
index e332a4c653..e99c4cf104 100644
--- a/tools/Makefile.unix
+++ b/tools/Makefile.unix
@@ -81,11 +81,6 @@ DIRLINK = $(TOPDIR)/tools/link.sh
 DIRUNLINK = $(TOPDIR)/tools/unlink.sh
 endif
 
-# This define is passed as EXTRAFLAGS for kernel-mode builds.  It is also passed
-# during PASS1 (but not PASS2) context and depend targets.
-
-KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
-
 # Process architecture and board-specific directories
 
 ARCH_DIR = arch/$(CONFIG_ARCH)
diff --git a/tools/Makefile.win b/tools/Makefile.win
index 5950f69690..8c302473bf 100644
--- a/tools/Makefile.win
+++ b/tools/Makefile.win
@@ -63,11 +63,6 @@ else
 export Q := @
 endif
 
-# This define is passed as EXTRAFLAGS for kernel-mode builds.  It is also passed
-# during PASS1 (but not PASS2) context and depend targets.
-
-KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
-
 # Process architecture and board-specific directories
 
 ARCH_DIR = arch\$(CONFIG_ARCH)