diff --git a/srcpkgs/z3/patches/fix-gcc6-typecast.patch b/srcpkgs/z3/patches/fix-gcc6-typecast.patch
index c8efb782d06..10456d05026 100644
--- a/srcpkgs/z3/patches/fix-gcc6-typecast.patch
+++ b/srcpkgs/z3/patches/fix-gcc6-typecast.patch
@@ -9,3 +9,14 @@
          if (!ok) exit(ERR_INTERNAL_FATAL); // happens if std::cin is eof or unattached.
          switch(result) {
          case 'C':
+--- src/util/mpz.cpp	2015-10-05 14:07:19.000000000 +0200
++++ src/util/mpz.cpp	2016-09-23 10:10:19.116642705 +0200
+@@ -134,7 +134,7 @@
+ #endif
+     
+     mpz one(1);
+-    set(m_two64, UINT64_MAX);
++    set(m_two64, static_cast<uint64>(UINT64_MAX));
+     add(m_two64, one, m_two64);
+ }
+