diff --git a/m4/fptools_set_haskell_platform_vars.m4 b/m4/fptools_set_haskell_platform_vars.m4
index 1c4976bfbca3e546c6d4b1044c2f4833b1890332..8cc721d79b8ffbbe4369498b87bf6c957054fede 100644
--- a/m4/fptools_set_haskell_platform_vars.m4
+++ b/m4/fptools_set_haskell_platform_vars.m4
@@ -82,7 +82,7 @@ AC_DEFUN([FPTOOLS_SET_HASKELL_PLATFORM_VARS_SHELL_FUNCTIONS],
         solaris2)
             test -z "[$]2" || eval "[$]2=OSSolaris2"
             ;;
-        mingw32|windows)
+        mingw32|mingw64|windows)
             test -z "[$]2" || eval "[$]2=OSMinGW32"
             ;;
         freebsd)
diff --git a/m4/ghc_convert_os.m4 b/m4/ghc_convert_os.m4
index 586b33d09b52a5c5a49d43b47c483e8ddf45b2b2..b39c20c6de75dc84c4a103101a44044e2b904ff9 100644
--- a/m4/ghc_convert_os.m4
+++ b/m4/ghc_convert_os.m4
@@ -22,7 +22,7 @@ AC_DEFUN([GHC_CONVERT_OS],[
       openbsd*)
         $3="openbsd"
         ;;
-      windows|mingw32)
+      windows|mingw32|mingw64)
         $3="mingw32"
         ;;
       # As far as I'm aware, none of these have relevant variants