diff --git a/CMakeLists.txt b/CMakeLists.txt
index db478f73..f0c50bf2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -27,7 +27,12 @@ if (HAVE_STD_CPP11_FLAG)
   check_cxx_source_compiles("
     #include <cmath>
     int main() {}" FMT_CPP11_CMATH)
-  if (FMT_CPP11_CMATH)
+  # Check if including <unistd.h> works with -std=c++11.
+  # It may not in MinGW due to bug http://sourceforge.net/p/mingw/bugs/2024/.
+  check_cxx_source_compiles("
+    #include <unistd.h>
+    int main() {}" FMT_CPP11_IO_H)
+  if (FMT_CPP11_CMATH AND FMT_CPP11_IO_H)
     set(CPP11_FLAG -std=c++11)
   endif ()
   set(CMAKE_REQUIRED_FLAGS )