--- a/libraries/Cabal/Cabal/src/Distribution/Simple/PreProcess.hs
+++ b/libraries/Cabal/Cabal/src/Distribution/Simple/PreProcess.hs
@@ -780,7 +780,7 @@ platformDefines lbi =
       Android -> ["android"]
       Ghcjs -> ["ghcjs"]
       Wasi -> ["wasi"]
-      Hurd -> ["hurd"]
+      Hurd -> ["gnu"]
       Haiku -> ["haiku"]
       OtherOS _ -> []
     archStr = case hostArch of
--- a/libraries/ghc-platform/src/GHC/Platform/ArchOS.hs
+++ b/libraries/ghc-platform/src/GHC/Platform/ArchOS.hs
@@ -157,7 +157,7 @@ stringEncodeOS = \case
   OSHaiku     -> "haiku"
   OSQNXNTO    -> "nto-qnx"
   OSAIX       -> "aix"
-  OSHurd      -> "hurd"
+  OSHurd      -> "gnu"
   OSWasi      -> "wasi"
   OSGhcjs     -> "ghcjs"
 
