diff --git a/pkgs/development/libraries/mpfr/default.nix b/pkgs/development/libraries/mpfr/default.nix
index e1809d544d1..581f956b0af 100644
--- a/pkgs/development/libraries/mpfr/default.nix
+++ b/pkgs/development/libraries/mpfr/default.nix
@@ -14,6 +14,7 @@ stdenv.mkDerivation rec {
   propagatedBuildInputs = [ gmp ];
 
   configureFlags =
+    stdenv.lib.optional stdenv.isSunOS "--disable-thread-safe" ++
     stdenv.lib.optional stdenv.is64bit "--with-pic";
 
   doCheck = true;