diff --git a/libs/libc/Makefile b/libs/libc/Makefile
index f4b6cea3873..de648dc3751 100644
--- a/libs/libc/Makefile
+++ b/libs/libc/Makefile
@@ -38,11 +38,7 @@
 # CFLAGS
 
 ifneq ($(CONFIG_BUILD_FLAT),y)
-ifeq ($(CONFIG_WINDOWS_NATIVE),y)
-  KDEFINE = ${shell $(TOPDIR)\tools\define.bat "$(CC)" __KERNEL__}
-else
-  KDEFINE = ${shell $(TOPDIR)/tools/define.sh "$(CC)" __KERNEL__}
-endif
+  KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
 endif
 
 # Sources and paths
diff --git a/libs/libnx/Makefile b/libs/libnx/Makefile
index c0109dc07d5..cdf9b4fa148 100644
--- a/libs/libnx/Makefile
+++ b/libs/libnx/Makefile
@@ -38,11 +38,7 @@
 # CFLAGS
 
 ifneq ($(CONFIG_BUILD_FLAT),y)
-ifeq ($(CONFIG_WINDOWS_NATIVE),y)
-  KDEFINE = ${shell $(TOPDIR)\tools\define.bat "$(CC)" __KERNEL__}
-else
-  KDEFINE = ${shell $(TOPDIR)/tools/define.sh "$(CC)" __KERNEL__}
-endif
+  KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
 endif
 
 # Sources and paths
diff --git a/mm/Makefile b/mm/Makefile
index bc4ce9aff4c..7f1dbcfb6a8 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -41,11 +41,7 @@ DELIM := $(strip /)
 # CFLAGS
 
 ifneq ($(CONFIG_BUILD_FLAT),y)
-ifeq ($(CONFIG_WINDOWS_NATIVE),y)
-  KDEFINE = ${shell $(TOPDIR)\tools\define.bat "$(CC)" __KERNEL__}
-else
-  KDEFINE = ${shell $(TOPDIR)/tools/define.sh "$(CC)" __KERNEL__}
-endif
+  KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
 endif
 
 # Sources and paths
diff --git a/tools/Config.mk b/tools/Config.mk
index 2a45f5b0e6b..0f6212890df 100644
--- a/tools/Config.mk
+++ b/tools/Config.mk
@@ -93,8 +93,10 @@ endif
 #   CONFIG_WINDOWS_NATIVE - Defined for a Windows native build
 
 ifeq ($(CONFIG_WINDOWS_NATIVE),y)
+  DEFINE = "$(TOPDIR)\tools\define.bat"
   INCDIR = "$(TOPDIR)\tools\incdir.bat"
 else
+  DEFINE = "$(TOPDIR)/tools/define.sh"
   INCDIR = "$(TOPDIR)/tools/incdir.sh"
 endif
 
diff --git a/tools/Makefile.unix b/tools/Makefile.unix
index 917ea0dbdf8..cb4c0cc4c15 100644
--- a/tools/Makefile.unix
+++ b/tools/Makefile.unix
@@ -81,7 +81,7 @@ endif
 # This define is passed as EXTRADEFINES for kernel-mode builds.  It is also passed
 # during PASS1 (but not PASS2) context and depend targets.
 
-KDEFINE = ${shell $(TOPDIR)/tools/define.sh "$(CC)" __KERNEL__}
+KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
 
 # Process architecture and board-specific directories
 
diff --git a/tools/Makefile.win b/tools/Makefile.win
index 6ef5bdc65f2..be4fd82a60c 100644
--- a/tools/Makefile.win
+++ b/tools/Makefile.win
@@ -66,7 +66,7 @@ endif
 # This define is passed as EXTRADEFINES for kernel-mode builds.  It is also passed
 # during PASS1 (but not PASS2) context and depend targets.
 
-KDEFINE = ${shell $(TOPDIR)\tools\define.bat "$(CC)" __KERNEL__}
+KDEFINE = ${shell $(DEFINE) "$(CC)" __KERNEL__}
 
 # Process architecture and board-specific directories