diff --git a/fetch b/fetch
index 3227b888b2..ca617e50c3 100755
--- a/fetch
+++ b/fetch
@@ -9,16 +9,13 @@ base_dir=$(dirname "$0")
 # standalone, but allow other PATH manipulations to take priority.
 PATH=$PATH:$base_dir
 
-# MINGW will equal 0 if we're running on Windows under MinGW.
-MINGW=$(uname -s | grep MINGW > /dev/null; echo $?)
-
 if [[ $GCLIENT_PY3 == 1 ]]; then
   # Explicitly run on Python 3
   PYTHONDONTWRITEBYTECODE=1 exec vpython3 "$base_dir/fetch.py" "$@"
 elif [[ $GCLIENT_PY3 == 0 ]]; then
   # Explicitly run on Python 2
   PYTHONDONTWRITEBYTECODE=1 exec vpython "$base_dir/fetch.py" "$@"
-elif [[ $MINGW = 0 ]]; then
+elif [[ $(uname -s) = MINGW* || $(uname -s) = CYGWIN* ]]; then
   # Run on Python 2 on Windows for now, allows default to be flipped.
   PYTHONDONTWRITEBYTECODE=1 exec vpython "$base_dir/fetch.py" "$@"
 else
diff --git a/gclient b/gclient
index 8937334457..003e190bbb 100755
--- a/gclient
+++ b/gclient
@@ -26,16 +26,13 @@ fi
 # standalone, but allow other PATH manipulations to take priority.
 PATH=$PATH:$base_dir
 
-# MINGW will equal 0 if we're running on Windows under MinGW.
-MINGW=$(uname -s | grep MINGW > /dev/null; echo $?)
-
 if [[ $GCLIENT_PY3 == 1 ]]; then
   # Explicitly run on Python 3
   PYTHONDONTWRITEBYTECODE=1 exec vpython3 "$base_dir/gclient.py" "$@"
 elif [[ $GCLIENT_PY3 == 0 ]]; then
   # Explicitly run on Python 2
   PYTHONDONTWRITEBYTECODE=1 exec vpython "$base_dir/gclient.py" "$@"
-elif [[ $MINGW = 0 ]]; then
+elif [[ $(uname -s) = MINGW* || $(uname -s) = CYGWIN* ]]; then
   # Run on Python 2 on Windows for now, allows default to be flipped.
   PYTHONDONTWRITEBYTECODE=1 exec vpython "$base_dir/gclient.py" "$@"
 else
diff --git a/python_runner.sh b/python_runner.sh
index 50deb20de2..60267281f6 100755
--- a/python_runner.sh
+++ b/python_runner.sh
@@ -48,16 +48,13 @@ SCRIPT="${SCRIPT-${BASENAME//-/_}.py}"
 # standalone, but allow other PATH manipulations to take priority.
 PATH=$PATH:$DEPOT_TOOLS
 
-# MINGW will equal 0 if we're running on Windows under MinGW.
-MINGW=$(uname -s | grep MINGW > /dev/null; echo $?)
-
 if [[ $GCLIENT_PY3 = 1 ]]; then
   # Explicitly run on Python 3
   vpython3 "$DEPOT_TOOLS/$SCRIPT" "$@"
 elif [[ $GCLIENT_PY3 = 0 ]]; then
   # Explicitly run on Python 2
   vpython "$DEPOT_TOOLS/$SCRIPT" "$@"
-elif [[ $MINGW = 0 ]]; then
+elif [[ $(uname -s) = MINGW* || $(uname -s) = CYGWIN* ]]; then
   # Run on Python 2 on Windows for now, allows default to be flipped.
   vpython "$DEPOT_TOOLS/$SCRIPT" "$@"
 else
diff --git a/roll-dep b/roll-dep
index 7016ee38df..cde993eda4 100755
--- a/roll-dep
+++ b/roll-dep
@@ -9,16 +9,13 @@ base_dir=$(dirname "$0")
 # standalone, but allow other PATH manipulations to take priority.
 PATH=$PATH:$base_dir
 
-# MINGW will equal 0 if we're running on Windows under MinGW.
-MINGW=$(uname -s | grep MINGW > /dev/null; echo $?)
-
 if [[ $GCLIENT_PY3 = 1 ]]; then
   # Explicitly run on Python 3
   PYTHONDONTWRITEBYTECODE=1 exec vpython3 "$base_dir/roll_dep.py" "$@"
 elif [[ $GCLIENT_PY3 = 0 ]]; then
   # Explicitly run on Python 2
   PYTHONDONTWRITEBYTECODE=1 exec vpython "$base_dir/roll_dep.py" "$@"
-elif [[ $MINGW = 0 ]]; then
+elif [[ $(uname -s) = MINGW* || $(uname -s) = CYGWIN* ]]; then
   # Run on Python 2 on Windows for now, allows default to be flipped.
   PYTHONDONTWRITEBYTECODE=1 exec vpython "$base_dir/roll_dep.py" "$@"
 else
diff --git a/vpython3 b/vpython3
index b8a8334a6a..91a0625170 100755
--- a/vpython3
+++ b/vpython3
@@ -39,12 +39,9 @@ base_dir=$(dirname "$0")
 source "$base_dir/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
-# MINGW will equal 0 if we're running on Windows under MinGW.
-MINGW=$(uname -s | grep MINGW > /dev/null; echo $?)
-
 # If Python bootstrapping is not disabled, make sure Python has been
 # bootstrapped and add it to the front of PATH.
-if [[ $MINGW = 0 ]]; then
+if [[ $(uname -s) = MINGW* || $(uname -s) = CYGWIN* ]]; then
   cmd.exe //c $0.bat "$@"
 elif [[ $DEPOT_TOOLS_BOOTSTRAP_PYTHON3 != 0 ]]; then
   if [[ ! -e "$base_dir/python3_bin_reldir.txt" ]]; then