diff --git a/makefile b/makefile
index ad310ccb835..a690b680f6b 100644
--- a/makefile
+++ b/makefile
@@ -340,8 +340,14 @@ ifeq ($(TARGETOS),os2)
 EXE = .exe
 endif
 
-ifndef BUILD_EXE
-BUILD_EXE = $(EXE)
+# extension for build tools
+BUILD_EXE = 
+
+ifeq ($(OS),Windows_NT)
+BUILD_EXE = .exe
+endif
+ifneq ($(OS2_SHELL),)
+BUILD_EXE = .exe
 endif
 
 # compiler, linker and utilities
@@ -350,7 +356,7 @@ AR = @ar
 CC = @gcc
 LD = @g++
 endif
-MD = -mkdir$(EXE)
+MD = -mkdir$(BUILD_EXE)
 RM = @rm -f
 OBJDUMP = @objdump
 PYTHON = @python
diff --git a/src/build/build.mak b/src/build/build.mak
index 9b7a8d2c98f..900acb20632 100644
--- a/src/build/build.mak
+++ b/src/build/build.mak
@@ -31,7 +31,7 @@ PNG2BDC = $(PNG2BDC_TARGET)
 VERINFO = $(VERINFO_TARGET)
 
 ifneq ($(TERM),cygwin)
-ifeq ($(TARGETOS),win32)
+ifeq ($(OS),Windows_NT)
 MAKEDEP = $(subst /,\,$(MAKEDEP_TARGET))
 MAKEMAK = $(subst /,\,$(MAKEMAK_TARGET))
 MAKELIST = $(subst /,\,$(MAKELIST_TARGET))