diff --git a/shell.nix b/shell.nix
index 69ae19f..ce92c42 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,6 +1,6 @@
 with import <nixpkgs> { };
 haskell.lib.buildStackProject {
-   ghc = haskell.packages.ghc843.ghc;
+   ghc = haskell.packages.ghc844.ghc;
    name = "orgstat";
    # firefox for xdg-open
    buildInputs = [ zlib git openssh gnupg gnupg1compat xdg_utils firefox gmp ];
diff --git a/stack.yaml b/stack.yaml
index 4011d30..5ebf56b 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,4 +1,4 @@
-resolver: lts-12.5
+resolver: lts-12.18
 
 nix:
   shell-file: shell.nix