diff --git a/pkgs/applications/science/math/giac/default.nix b/pkgs/applications/science/math/giac/default.nix
index 2823165d022..4ad498e5922 100644
--- a/pkgs/applications/science/math/giac/default.nix
+++ b/pkgs/applications/science/math/giac/default.nix
@@ -9,11 +9,11 @@ assert enableGUI -> libGLU_combined != null && xorg != null && fltk != null;
 stdenv.mkDerivation rec {
   name = "${attr}-${version}";
   attr = if enableGUI then "giac-with-xcas" else "giac";
-  version = "1.4.9-59"; # TODO try to remove preCheck phase on upgrade
+  version = "1.5.0-21"; # TODO try to remove preCheck phase on upgrade
 
   src = fetchurl {
     url = "https://www-fourier.ujf-grenoble.fr/~parisse/debian/dists/stable/main/source/giac_${version}.tar.gz";
-    sha256 = "0dv5p5y6gkrsmz3xa7fw87rjyabwdwk09mqb09kb7gai9n9dgayk";
+    sha256 = "1b9khiv0mk2xzw1rblm2jy6qsf8y6f9k7qy15sxpb21d72hzzbl2";
   };
 
   patches = stdenv.lib.optionals (!enableGUI) [
diff --git a/pkgs/applications/science/math/sage/patches/giac-1.5.0.patch b/pkgs/applications/science/math/sage/patches/giac-1.5.0.patch
new file mode 100644
index 00000000000..58090b241d2
--- /dev/null
+++ b/pkgs/applications/science/math/sage/patches/giac-1.5.0.patch
@@ -0,0 +1,14 @@
+--- a/src/sage/interfaces/giac.py	2018-12-08 22:11:56.285500644 +0100
++++ b/src/sage/interfaces/giac.py	2018-12-08 22:11:56.285500644 +0100
+@@ -617,10 +617,7 @@
+             '4\n3'
+             sage: s='g(x):={\nx+1;\nx+2;\n}'
+             sage: giac(s)
+-            (x)->{
+-            x+1;
+-            x+2;
+-            }
++            (x)->[x+1,x+2]
+             sage: giac.g(5)
+             7
+         """
diff --git a/pkgs/applications/science/math/sage/sage-src.nix b/pkgs/applications/science/math/sage/sage-src.nix
index 5d729d9c5fd..5dc73e26a59 100644
--- a/pkgs/applications/science/math/sage/sage-src.nix
+++ b/pkgs/applications/science/math/sage/sage-src.nix
@@ -79,6 +79,9 @@ stdenv.mkDerivation rec {
     # https://trac.sagemath.org/ticket/25260
     ./patches/numpy-1.15.1.patch
 
+    # https://trac.sagemath.org/ticket/26315
+    ./patches/giac-1.5.0.patch
+
     # needed for ntl update
     # https://trac.sagemath.org/ticket/25532
     (fetchpatch {