diff --git a/pkgs/development/compilers/gerbil/build.nix b/pkgs/development/compilers/gerbil/build.nix
new file mode 100644
index 000000000000..5609de15d4cb
--- /dev/null
+++ b/pkgs/development/compilers/gerbil/build.nix
@@ -0,0 +1,88 @@
+{ stdenv, lib, makeStaticLibraries,
+  coreutils, rsync, bash,
+  openssl, zlib, sqlite, libxml2, libyaml, mysql, lmdb, leveldb, postgresql,
+  version, git-version, GAMBIT, SRC }:
+
+# TODO: distinct packages for gerbil-release and gerbil-devel
+# TODO: make static compilation work
+
+stdenv.mkDerivation rec {
+  name    = "gerbil-${version}";
+  src     = SRC;
+
+  # Use makeStaticLibraries to enable creation of statically linked binaries
+  buildInputs_libraries = [ openssl zlib sqlite libxml2 libyaml mysql.connector-c lmdb leveldb postgresql ];
+  buildInputs_staticLibraries = map makeStaticLibraries buildInputs_libraries;
+
+  buildInputs = [ GAMBIT coreutils rsync bash ]
+    ++ buildInputs_libraries ++ buildInputs_staticLibraries;
+
+  NIX_CFLAGS_COMPILE = [ "-I${mysql.connector-c}/include/mysql" "-L${mysql.connector-c}/lib/mysql" ];
+
+  postPatch = ''
+    echo '(define (gerbil-version-string) "v${git-version}")' > src/gerbil/runtime/gx-version.scm
+
+    patchShebangs .
+
+    find . -type f -executable -print0 | while IFS= read -r -d ''$'\0' f; do
+      substituteInPlace "$f" --replace '#!/usr/bin/env' '#!${coreutils}/bin/env'
+    done
+
+    cat > etc/gerbil_static_libraries.sh <<EOF
+#OPENSSL_LIBCRYPTO=${makeStaticLibraries openssl}/lib/libcrypto.a # MISSING!
+#OPENSSL_LIBSSL=${makeStaticLibraries openssl}/lib/libssl.a # MISSING!
+ZLIB=${makeStaticLibraries zlib}/lib/libz.a
+# SQLITE=${makeStaticLibraries sqlite}/lib/sqlite.a # MISSING!
+# LIBXML2=${makeStaticLibraries libxml2}/lib/libxml2.a # MISSING!
+# YAML=${makeStaticLibraries libyaml}/lib/libyaml.a # MISSING!
+MYSQL=${makeStaticLibraries mysql.connector-c}/lib/mariadb/libmariadb.a
+# LMDB=${makeStaticLibraries lmdb}/lib/mysql/libmysqlclient_r.a # MISSING!
+LEVELDB=${makeStaticLibraries lmdb}/lib/libleveldb.a
+EOF
+  '';
+
+  buildPhase = ''
+    runHook preBuild
+
+    # Enable all optional libraries
+    substituteInPlace "src/std/build-features.ss" --replace '#f' '#t'
+
+    # gxprof testing uses $HOME/.cache/gerbil/gxc
+    export HOME=$$PWD
+
+    # Build, replacing make by build.sh
+    ( cd src && sh build.sh )
+
+    runHook postBuild
+  '';
+
+  installPhase = ''
+    runHook preInstall
+    mkdir -p $out/
+    cp -fa bin lib etc doc $out/
+
+    cat > $out/bin/gxi <<EOF
+#!${bash}/bin/bash -e
+export GERBIL_HOME=$out
+case "\$1" in -:*) GSIOPTIONS=\$1 ; shift ;; esac
+if [[ \$# = 0 ]] ; then
+  exec ${GAMBIT}/bin/gsi \$GSIOPTIONS \$GERBIL_HOME/lib/gxi-init \$GERBIL_HOME/lib/gxi-interactive - ;
+else
+  exec ${GAMBIT}/bin/gsi \$GSIOPTIONS \$GERBIL_HOME/lib/gxi-init "\$@"
+fi
+EOF
+    runHook postInstall
+  '';
+
+  dontStrip = true;
+
+  meta = {
+    description = "Gerbil Scheme";
+    homepage    = "https://github.com/vyzo/gerbil";
+    license     = stdenv.lib.licenses.lgpl2;
+    # NB regarding platforms: only actually tested on Linux, *should* work everywhere,
+    # but *might* need adaptation e.g. on macOS. Please report success and/or failure to fare.
+    platforms   = stdenv.lib.platforms.unix;
+    maintainers = with stdenv.lib.maintainers; [ fare ];
+  };
+}
diff --git a/pkgs/development/compilers/gerbil/default.nix b/pkgs/development/compilers/gerbil/default.nix
index 555dbbfe460e..eaab0e71d3bd 100644
--- a/pkgs/development/compilers/gerbil/default.nix
+++ b/pkgs/development/compilers/gerbil/default.nix
@@ -1,91 +1,11 @@
-{ stdenv, lib, fetchurl, fetchgit, makeStaticLibraries, gambit,
-  coreutils, rsync, bash,
-  openssl, zlib, sqlite, libxml2, libyaml, mysql, lmdb, leveldb, postgresql }:
-
-# TODO: distinct packages for gerbil-release and gerbil-devel
-# TODO: make static compilation work
-
-stdenv.mkDerivation rec {
-  name    = "gerbil-${version}";
+{ callPackage, fetchurl, gambit }:
 
+callPackage ./build.nix {
   version = "0.12-RELEASE";
-  src = fetchgit {
-    url = "https://github.com/vyzo/gerbil.git";
-    rev = "5618892d7939e1cb4ef5247912e0bc1ec99f6b52";
-    sha256 = "0b2valahf5k81r4sp6y12d44fb286p92s7k6dphij0kmvg0dp818";
-  };
-
-  # Use makeStaticLibraries to enable creation of statically linked binaries
-  buildInputs_libraries = [ openssl zlib sqlite libxml2 libyaml mysql.connector-c lmdb leveldb postgresql ];
-  buildInputs_staticLibraries = map makeStaticLibraries buildInputs_libraries;
-
-  buildInputs = [ gambit coreutils rsync bash ]
-    ++ buildInputs_libraries ++ buildInputs_staticLibraries;
-
-  NIX_CFLAGS_COMPILE = [ "-I${mysql.connector-c}/include/mysql" "-L${mysql.connector-c}/lib/mysql" ];
-
-  postPatch = ''
-    echo '(define (gerbil-version-string) "v${version}")' > src/gerbil/runtime/gx-version.scm
-
-    patchShebangs .
-
-    find . -type f -executable -print0 | while IFS= read -r -d ''$'\0' f; do
-      substituteInPlace "$f" --replace '#!/usr/bin/env' '#!${coreutils}/bin/env'
-    done
-
-    cat > etc/gerbil_static_libraries.sh <<EOF
-#OPENSSL_LIBCRYPTO=${makeStaticLibraries openssl}/lib/libcrypto.a # MISSING!
-#OPENSSL_LIBSSL=${makeStaticLibraries openssl}/lib/libssl.a # MISSING!
-ZLIB=${makeStaticLibraries zlib}/lib/libz.a
-# SQLITE=${makeStaticLibraries sqlite}/lib/sqlite.a # MISSING!
-# LIBXML2=${makeStaticLibraries libxml2}/lib/libxml2.a # MISSING!
-# YAML=${makeStaticLibraries libyaml}/lib/libyaml.a # MISSING!
-MYSQL=${makeStaticLibraries mysql.connector-c}/lib/mariadb/libmariadb.a
-# LMDB=${makeStaticLibraries lmdb}/lib/mysql/libmysqlclient_r.a # MISSING!
-LEVELDB=${makeStaticLibraries lmdb}/lib/libleveldb.a
-EOF
-  '';
-
-  buildPhase = ''
-    runHook preBuild
-
-    # Enable all optional libraries
-    substituteInPlace "src/std/build-features.ss" --replace '#f' '#t'
-
-    # gxprof testing uses $HOME/.cache/gerbil/gxc
-    export HOME=$$PWD
-
-    # Build, replacing make by build.sh
-    ( cd src && sh build.sh )
-
-    runHook postBuild
-  '';
-
-  installPhase = ''
-    runHook preInstall
-    mkdir -p $out/
-    cp -fa bin lib etc doc $out/
-
-    cat > $out/bin/gxi <<EOF
-#!${bash}/bin/bash -e
-export GERBIL_HOME=$out
-case "\$1" in -:*) GSIOPTIONS=\$1 ; shift ;; esac
-if [[ \$# = 0 ]] ; then
-  exec ${gambit}/bin/gsi \$GSIOPTIONS \$GERBIL_HOME/lib/gxi-init \$GERBIL_HOME/lib/gxi-interactive - ;
-else
-  exec ${gambit}/bin/gsi \$GSIOPTIONS \$GERBIL_HOME/lib/gxi-init "\$@"
-fi
-EOF
-    runHook postInstall
-  '';
-
-  dontStrip = true;
-
-  meta = {
-    description = "Gerbil Scheme";
-    homepage    = "https://github.com/vyzo/gerbil";
-    license     = stdenv.lib.licenses.lgpl2;
-    platforms   = stdenv.lib.platforms.unix;
-    maintainers = with stdenv.lib.maintainers; [ fare ];
+  git-version = "0.12";
+  GAMBIT = gambit;
+  SRC = fetchurl {
+    url = "https://github.com/vyzo/gerbil/archive/v0.12.tar.gz";
+    sha256 = "0nigr3mgrzai57q2jqac8f39zj8rcmic3277ynyzlgm8hhps71pq";
   };
 }
diff --git a/pkgs/development/compilers/gerbil/unstable.nix b/pkgs/development/compilers/gerbil/unstable.nix
new file mode 100644
index 000000000000..ec36f42d86e6
--- /dev/null
+++ b/pkgs/development/compilers/gerbil/unstable.nix
@@ -0,0 +1,12 @@
+{ callPackage, fetchgit, gambit-unstable }:
+
+callPackage ./build.nix {
+  version = "unstable-2018-04-03";
+  git-version = "0.13-DEV-357-ge61318dc";
+  GAMBIT = gambit-unstable;
+  SRC = fetchgit {
+    url = "https://github.com/vyzo/gerbil.git";
+    rev = "e61318dcaa3a9c843e2cf259e67851f240e4beda";
+    sha256 = "1xd7yxiramifdxgp6b3s24z6nkkmy5h4a6pkchvy4w358qv1vqin";
+  };
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 8b8b9fdb1c95..c1c873d05681 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -5968,6 +5968,7 @@ with pkgs;
   gambit = callPackage ../development/compilers/gambit { };
   gambit-unstable = callPackage ../development/compilers/gambit/unstable.nix { };
   gerbil = callPackage ../development/compilers/gerbil { };
+  gerbil-unstable = callPackage ../development/compilers/gerbil/unstable.nix { };
 
   gccFun = callPackage ../development/compilers/gcc/7;
   gcc = gcc7;