diff --git a/appveyor.yml b/appveyor.yml
index dd2c02ac4..fb8ea3793 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -187,6 +187,9 @@
   version: 1.0.{build}
   environment:
     matrix:
+    - COMPILER: "gcc"
+      HOST:     "cygwin"
+      PLATFORM: "x64"
     - COMPILER: "gcc"
       HOST:     "mingw"
       PLATFORM: "x64"
@@ -220,6 +223,14 @@
   install:
   - ECHO Installing %COMPILER% %PLATFORM% %CONFIGURATION%
   - SET PATH_ORIGINAL=%PATH%
+  - if [%HOST%]==[cygwin] (
+      ECHO Installing Cygwin Packages &&
+      C:\cygwin64\setup-x86_64.exe -qnNdO -R "C:\cygwin64" -g -P ^
+        gcc-g++,^
+        gcc,^
+        cmake,^
+        make
+    )
   - if [%HOST%]==[mingw] (
       SET "PATH_MINGW32=C:\mingw-w64\i686-6.3.0-posix-dwarf-rt_v5-rev1\mingw32\bin" &&
       SET "PATH_MINGW64=C:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1\mingw64\bin" &&
@@ -232,6 +243,16 @@
 
   build_script:
   - ECHO Building %COMPILER% %PLATFORM% %CONFIGURATION%
+  - if [%HOST%]==[cygwin] (
+      set CHERE_INVOKING=yes &&
+      set CC=%COMPILER% &&
+      C:\cygwin64\bin\bash --login -c "
+        set -e;
+        cd build/cmake;
+        CFLAGS='-Werror' cmake -G 'Unix Makefiles' .;
+        make -j4;
+      "
+    )
   - if [%HOST%]==[mingw] (
       ( if [%PLATFORM%]==[x64] (
         SET "PATH=%PATH_MINGW64%;%PATH_ORIGINAL%"
diff --git a/programs/platform.h b/programs/platform.h
index 64ecd21fc..31820631e 100644
--- a/programs/platform.h
+++ b/programs/platform.h
@@ -90,7 +90,7 @@ extern "C" {
      && ( defined(__unix__) || defined(__unix) \
        || defined(__midipix__) || defined(__VMS) || defined(__HAIKU__) )
 
-#    if defined(__linux__) || defined(__linux)
+#    if defined(__linux__) || defined(__linux) || defined(__CYGWIN__)
 #      ifndef _POSIX_C_SOURCE
 #        define _POSIX_C_SOURCE 200809L  /* feature test macro : https://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html */
 #      endif
@@ -123,11 +123,11 @@ extern "C" {
 ************************************************/
 #if (defined(__linux__) && (PLATFORM_POSIX_VERSION > 1)) \
  || (PLATFORM_POSIX_VERSION >= 200112L) \
- || defined(__DJGPP__) \
- || defined(__MSYS__)
+ || defined(__DJGPP__)
 #  include <unistd.h>   /* isatty */
+#  include <stdio.h>    /* fileno */
 #  define IS_CONSOLE(stdStream) isatty(fileno(stdStream))
-#elif defined(MSDOS) || defined(OS2) || defined(__CYGWIN__)
+#elif defined(MSDOS) || defined(OS2)
 #  include <io.h>       /* _isatty */
 #  define IS_CONSOLE(stdStream) _isatty(_fileno(stdStream))
 #elif defined(WIN32) || defined(_WIN32)