diff --git a/Makefile.rules b/Makefile.rules
index 01489a570f2..cb4abafd289 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -322,7 +322,13 @@ endif
 ifeq ($(ENABLE_CXX1Y),1)
   CXX.Flags += -std=c++1y
 else
-	CXX.Flags += -std=c++11
+  ifeq ($(HOST_OS), $(filter $(HOST_OS), Cygwin MingW))
+    # MinGW and Cygwin are a bit stricter and lack things like
+    # 'strdup', 'stricmp', etc in c++11 mode.
+    CXX.Flags += -std=gnu++11
+ else
+    CXX.Flags += -std=c++11
+ endif
 endif
 
 ifeq ($(ENABLE_WERROR),1)
diff --git a/cmake/modules/HandleLLVMOptions.cmake b/cmake/modules/HandleLLVMOptions.cmake
index ccf5f90f17c..319adf3f325 100644
--- a/cmake/modules/HandleLLVMOptions.cmake
+++ b/cmake/modules/HandleLLVMOptions.cmake
@@ -293,7 +293,13 @@ elseif( LLVM_COMPILER_IS_GCC_COMPATIBLE )
   else()
     check_cxx_compiler_flag("-std=c++11" CXX_SUPPORTS_CXX11)
     if (CXX_SUPPORTS_CXX11)
-      append("-std=c++11" CMAKE_CXX_FLAGS)
+      if (CYGWIN OR MINGW)
+        # MinGW and Cygwin are a bit stricter and lack things like
+        # 'strdup', 'stricmp', etc in c++11 mode.
+        append("-std=gnu++11" CMAKE_CXX_FLAGS)
+      else()
+        append("-std=c++11" CMAKE_CXX_FLAGS)
+      endif()
     else()
       message(FATAL_ERROR "LLVM requires C++11 support but the '-std=c++11' flag isn't supported.")
     endif()