diff --git a/pkgs/development/libraries/isl/0.14.1.nix b/pkgs/development/libraries/isl/0.14.1.nix
index 8936d6c5f3be..87243def1796 100644
--- a/pkgs/development/libraries/isl/0.14.1.nix
+++ b/pkgs/development/libraries/isl/0.14.1.nix
@@ -4,7 +4,10 @@ stdenv.mkDerivation rec {
   name = "isl-0.14.1";
 
   src = fetchurl {
-    url = "http://isl.gforge.inria.fr/${name}.tar.xz";
+    urls = [
+      "mirror://sourceforge/libisl/${name}.tar.xz"
+      "https://libisl.sourceforge.io/${name}.tar.xz"
+    ];
     sha256 = "0xa6xagah5rywkywn19rzvbvhfvkmylhcxr6z9z7bz29cpiwk0l8";
   };
 
diff --git a/pkgs/development/libraries/isl/0.17.1.nix b/pkgs/development/libraries/isl/0.17.1.nix
index a823b69fa27b..a066655d4a05 100644
--- a/pkgs/development/libraries/isl/0.17.1.nix
+++ b/pkgs/development/libraries/isl/0.17.1.nix
@@ -4,7 +4,10 @@ stdenv.mkDerivation rec {
   name = "isl-0.17.1";
 
   src = fetchurl {
-    url = "http://isl.gforge.inria.fr/${name}.tar.xz";
+    urls = [
+      "mirror://sourceforge/libisl/${name}.tar.xz"
+      "https://libisl.sourceforge.io/${name}.tar.xz"
+    ];
     sha256 = "be152e5c816b477594f4c6194b5666d8129f3a27702756ae9ff60346a8731647";
   };
 
diff --git a/pkgs/development/libraries/isl/0.20.0.nix b/pkgs/development/libraries/isl/0.20.0.nix
index c40b3d7be0b4..d68637ddbcde 100644
--- a/pkgs/development/libraries/isl/0.20.0.nix
+++ b/pkgs/development/libraries/isl/0.20.0.nix
@@ -4,7 +4,11 @@ stdenv.mkDerivation rec {
   name = "isl-0.20";
 
   src = fetchurl {
-    url = "http://isl.gforge.inria.fr/${name}.tar.xz";
+    urls = [
+      "mirror://sourceforge/libisl/${name}.tar.xz"
+      "https://libisl.sourceforge.io/${name}.tar.xz"
+    ];
+
     sha256 = "1akpgq0rbqbah5517blg2zlnfvjxfcl9cjrfc75nbcx5p2gnlnd5";
   };