diff --git a/pkgs/development/compilers/gambit/unstable.nix b/pkgs/development/compilers/gambit/unstable.nix
index 3ac4f5363195..7284e5b531d8 100644
--- a/pkgs/development/compilers/gambit/unstable.nix
+++ b/pkgs/development/compilers/gambit/unstable.nix
@@ -1,13 +1,13 @@
 { callPackage, fetchFromGitHub, gambit-support }:
 
 callPackage ./build.nix {
-  version = "unstable-2020-05-15";
-  git-version = "4.9.3-1109-g3c4d40de";
+  version = "unstable-2020-07-29";
+  git-version = "4.9.3-1232-gbba388b8";
   src = fetchFromGitHub {
     owner = "feeley";
     repo = "gambit";
-    rev = "3c4d40de908ae03ca0e3d854edc2234ef401b36c";
-    sha256 = "1c9a6rys2kiiqb79gvw29nv3dwwk6hmi1q4jk1whcx7mds7q5dvr";
+    rev = "bba388b80ca62a77883a8936d64b03316808696a";
+    sha256 = "0iqlp1mvxz8g32kqrqm0phnnp1i5c4jrapqh2wqwa8fh1vgnizg1";
   };
   gambit-params = gambit-support.unstable-params;
 }