diff --git a/Makefile b/Makefile
index 083f3bd..9c8cca2 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-ifeq ($(shell uname -o),Cygwin)
+ifeq ($(shell uname -s),CYGWIN*)
 WUT_ROOT := $(shell cygpath -w ${CURDIR})
 else
 WUT_ROOT := $(CURDIR)
diff --git a/rpl/common/rules.mk b/rpl/common/rules.mk
index ad385f9..b6f40ee 100644
--- a/rpl/common/rules.mk
+++ b/rpl/common/rules.mk
@@ -1,6 +1,6 @@
 .SUFFIXES:
 
-ifeq ($(shell uname -o),Cygwin)
+ifeq ($(shell uname -s),CYGWIN*)
 CUR_DIR := $(shell cygpath -w ${CURDIR})
 else
 CUR_DIR := $(CURDIR)
diff --git a/rules/ppc.mk b/rules/ppc.mk
index 61b5703..f0a1119 100644
--- a/rules/ppc.mk
+++ b/rules/ppc.mk
@@ -1,4 +1,4 @@
-ifeq ($(shell uname -o),Cygwin)
+ifeq ($(shell uname -s),CYGWIN*)
 WUT_ROOT := $(shell cygpath -w ${WUT_ROOT})
 else
 WUT_ROOT := $(WUT_ROOT)
diff --git a/samples/helloworld/Makefile b/samples/helloworld/Makefile
index 15f4008..13aec28 100644
--- a/samples/helloworld/Makefile
+++ b/samples/helloworld/Makefile
@@ -4,7 +4,7 @@ ifeq ($(strip $(WUT_ROOT)),)
 $(error "Please ensure WUT_ROOT is in your environment.")
 endif
 
-ifeq ($(shell uname -o),Cygwin)
+ifeq ($(shell uname -s),CYGWIN*)
 ROOT := $(shell cygpath -w ${CURDIR})
 WUT_ROOT := $(shell cygpath -w ${WUT_ROOT})
 else
diff --git a/samples/pong/Makefile b/samples/pong/Makefile
index ef9dadd..d90c68c 100644
--- a/samples/pong/Makefile
+++ b/samples/pong/Makefile
@@ -4,7 +4,7 @@ ifeq ($(strip $(WUT_ROOT)),)
 $(error "Please ensure WUT_ROOT is in your environment.")
 endif
 
-ifeq ($(shell uname -o),Cygwin)
+ifeq ($(shell uname -s),CYGWIN*)
 ROOT := $(shell cygpath -w ${CURDIR})
 WUT_ROOT := $(shell cygpath -w ${WUT_ROOT})
 else