diff --git a/pkgs/applications/video/aegisub/default.nix b/pkgs/applications/video/aegisub/default.nix
index a613ad1c5842..3df616824801 100644
--- a/pkgs/applications/video/aegisub/default.nix
+++ b/pkgs/applications/video/aegisub/default.nix
@@ -48,6 +48,9 @@ stdenv.mkDerivation rec {
 
   hardeningDisable = [ "bindnow" "relro" ];
 
+  # compat with icu61+ https://github.com/unicode-org/icu/blob/release-64-2/icu4c/readme.html#L554
+  CXXFLAGS = [ "-DU_USING_ICU_NAMESPACE=1" ];
+
   # this is fixed upstream though not yet in an officially released version,
   # should be fine remove on next release (if one ever happens)
   NIX_LDFLAGS = [
diff --git a/pkgs/development/libraries/languagemachines/libfolia.nix b/pkgs/development/libraries/languagemachines/libfolia.nix
index 395591be55be..a00c3be4193e 100644
--- a/pkgs/development/libraries/languagemachines/libfolia.nix
+++ b/pkgs/development/libraries/languagemachines/libfolia.nix
@@ -16,6 +16,9 @@ stdenv.mkDerivation {
   buildInputs = [ automake autoconf bzip2 libtool autoconf-archive libtar libxml2 icu languageMachines.ticcutils ];
   preConfigure = "sh bootstrap.sh";
 
+  # compat with icu61+ https://github.com/unicode-org/icu/blob/release-64-2/icu4c/readme.html#L554
+  CXXFLAGS = [ "-DU_USING_ICU_NAMESPACE=1" ];
+
   meta = with stdenv.lib; {
     description = "A C++ API for FoLiA documents; an XML-based linguistic annotation format.";
     homepage    = https://proycon.github.io/folia/;
diff --git a/pkgs/tools/filesystems/darling-dmg/default.nix b/pkgs/tools/filesystems/darling-dmg/default.nix
index e44d0d229052..4952036a860b 100644
--- a/pkgs/tools/filesystems/darling-dmg/default.nix
+++ b/pkgs/tools/filesystems/darling-dmg/default.nix
@@ -20,6 +20,9 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ cmake fuse openssl zlib bzip2 libxml2 icu ];
 
+  # compat with icu61+ https://github.com/unicode-org/icu/blob/release-64-2/icu4c/readme.html#L554
+  CXXFLAGS = [ "-DU_USING_ICU_NAMESPACE=1" ];
+
   meta = {
     homepage = http://www.darlinghq.org/;
     description = "Darling lets you open macOS dmgs on Linux";