diff --git a/pkgs/development/libraries/icu/base.nix b/pkgs/development/libraries/icu/base.nix
index b12e76a90a9..8a7cf8365a5 100644
--- a/pkgs/development/libraries/icu/base.nix
+++ b/pkgs/development/libraries/icu/base.nix
@@ -26,7 +26,9 @@ stdenv.mkDerivation {
   '';
 
   # https://sourceware.org/glibc/wiki/Release/2.26#Removal_of_.27xlocale.h.27
-  postPatch = "substituteInPlace i18n/digitlst.cpp --replace '<xlocale.h>' '<locale.h>'";
+  postPatch = if stdenv ? glibc
+    then "substituteInPlace i18n/digitlst.cpp --replace '<xlocale.h>' '<locale.h>'"
+    else null; # won't find locale_t on darwin
 
   inherit patchFlags patches;