diff --git a/pkgs/development/libraries/ptlib/default.nix b/pkgs/development/libraries/ptlib/default.nix
index f980a14aa41d..ae60a6f69d63 100644
--- a/pkgs/development/libraries/ptlib/default.nix
+++ b/pkgs/development/libraries/ptlib/default.nix
@@ -24,12 +24,16 @@ stdenv.mkDerivation rec {
     (fetchpatch { url = http://sources.debian.net/data/main/p/ptlib/2.10.11~dfsg-2.1/debian/patches/no-sslv3;
       sha256 = "172s1dnnrl54p9sf1nl7s475sm78rpw3p8jxi0pdx6izzl8hcdr0";
     })
-    (fetchpatch { url = http://sources.debian.net/data/main/p/ptlib/2.10.11~dfsg-2.1/debian/patches/gcc-5_support;
-      sha256 = "0pf2yj0150r4cnc6nv65mclrm3dillqh1xjk7m6gsjnk9b96i5d4";
-    })
     ./ptlib-2.10.11-glibc-2.26.patch
   ];
 
+  # fix typedef clashes with unixODBC>=2.3.5
+  postPatch = ''
+    substituteInPlace include/ptlib/unix/ptlib/contain.h \
+      --replace "typedef uintptr_t    UINT" "typedef unsigned int    UINT" \
+      --replace "typedef wchar_t                 WCHAR" "typedef unsigned short          WCHAR"
+  '';
+
   meta = with stdenv.lib; {
     description = "Portable Tools from OPAL VoIP";
     maintainers = [ maintainers.raskin ];