diff --git a/pkgs/development/compilers/gambit/unstable.nix b/pkgs/development/compilers/gambit/unstable.nix
index 169ddb5a6a31..85e940eea570 100644
--- a/pkgs/development/compilers/gambit/unstable.nix
+++ b/pkgs/development/compilers/gambit/unstable.nix
@@ -1,10 +1,11 @@
 { callPackage, fetchgit }:
 
 callPackage ./build.nix {
-  version = "unstable-2018-05-30";
+  version = "unstable-2018-08-06";
+# git-version = "4.8.9-77-g91a4ad2c";
   SRC = fetchgit {
     url = "https://github.com/feeley/gambit.git";
-    rev = "ffe8841b56330eb86fd794b16dc7f83914ecc7c5";
-    sha256 = "1xzkwa2f6zazybbgd5zynhr36krayhr29vsbras5ld63hkrxrp7q";
+    rev = "91a4ad2c28375f067adedcaa61f9d66a4b536f4f";
+    sha256 = "0px1ipvhh0hz8n38h6jv4y1nn163j8llvcy4l7p3hkdns5czwy1p";
   };
 }