diff --git a/pkgs/os-specific/darwin/by-name/ic/ICU/package.nix b/pkgs/os-specific/darwin/by-name/ic/ICU/package.nix
index f742f4743807..d2678d47b0bc 100644
--- a/pkgs/os-specific/darwin/by-name/ic/ICU/package.nix
+++ b/pkgs/os-specific/darwin/by-name/ic/ICU/package.nix
@@ -3,7 +3,7 @@
   bootstrapStdenv,
   buildPackages,
   fetchpatch2,
-  icu76, # The ICU version should correspond to the same one used by Apple’s ICU package
+  icu78, # The ICU version should correspond to the same one used by Apple’s ICU package
   mkAppleDerivation,
   python3,
   stdenvNoCC,
@@ -40,9 +40,11 @@ let
 
     patches = [
       # Skip MessageFormatTest test, which is known to crash sometimes and should be suppressed if it does.
-      ./patches/suppress-icu-check-crash.patch
+      ./patches/0001-suppress-icu-check-crash.patch
     ];
 
+    patchFlags = [ "-p4" ];
+
     preConfigure = ''
       sed -i -e "s|/bin/sh|${stdenv.shell}|" configure
       patchShebangs --build .
@@ -118,7 +120,7 @@ let
 
           # Add missing test data. It’s not included in the source release.
           chmod u+w "$NIX_BUILD_TOP/source/icu"
-          tar -C "$NIX_BUILD_TOP/source" -axf ${lib.escapeShellArg icu76.src} icu/testdata
+          tar -C "$NIX_BUILD_TOP/source" -axf ${lib.escapeShellArg icu78.src} icu/testdata
         ''
         + lib.optionalString stdenv.hostPlatform.isx86_64 ''
           # These tests fail under Rosetta 2 with a floating-point exception.
diff --git a/pkgs/os-specific/darwin/by-name/ic/ICU/patches/0001-suppress-icu-check-crash.patch b/pkgs/os-specific/darwin/by-name/ic/ICU/patches/0001-suppress-icu-check-crash.patch
new file mode 100644
index 000000000000..b9018766b838
--- /dev/null
+++ b/pkgs/os-specific/darwin/by-name/ic/ICU/patches/0001-suppress-icu-check-crash.patch
@@ -0,0 +1,25 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Randy Eckenrode <randy@largeandhighquality.com>
+Date: Fri, 8 May 2026 21:00:49 -0400
+Subject: [PATCH] suppress-icu-check-crash
+
+---
+ icu/icu4c/source/test/cintltst/cmsgtst.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/icu/icu4c/source/test/cintltst/cmsgtst.c b/icu/icu4c/source/test/cintltst/cmsgtst.c
+index 16263b5c7..fccc2753d 100644
+--- a/icu/icu4c/source/test/cintltst/cmsgtst.c
++++ b/icu/icu4c/source/test/cintltst/cmsgtst.c
+@@ -231,7 +231,7 @@ static void MessageFormatTest( void )
+                         austrdup(result), austrdup(testResultStrings[i]) );
+                 }
+ 
+-#if (U_PLATFORM == U_PF_LINUX || U_PLATFORM == U_PF_QNX) /* add platforms here .. */
++#if (U_PLATFORM == U_PF_LINUX || U_PLATFORM == U_PF_DARWIN || U_PLATFORM == U_PF_QNX) /* add platforms here .. */
+                 log_verbose("Skipping potentially crashing test for mismatched varargs.\n");
+ #else
+                 log_verbose("Note: the next is a platform dependent test. If it crashes, add an exclusion for your platform near %s:%d\n", __FILE__, __LINE__); 
+-- 
+2.51.2
+
diff --git a/pkgs/os-specific/darwin/by-name/ic/ICU/patches/suppress-icu-check-crash.patch b/pkgs/os-specific/darwin/by-name/ic/ICU/patches/suppress-icu-check-crash.patch
deleted file mode 100644
index 23a5ac307c80..000000000000
--- a/pkgs/os-specific/darwin/by-name/ic/ICU/patches/suppress-icu-check-crash.patch
+++ /dev/null
@@ -1,13 +0,0 @@
-diff --git a/test/cintltst/cmsgtst.c b/test/cintltst/cmsgtst.c
-index cb328707..1073e6c1 100644
---- a/test/cintltst/cmsgtst.c
-+++ b/test/cintltst/cmsgtst.c
-@@ -231,7 +231,7 @@ static void MessageFormatTest( void )
-                         austrdup(result), austrdup(testResultStrings[i]) );
-                 }
- 
--#if (U_PLATFORM == U_PF_LINUX) /* add platforms here .. */
-+#if (U_PLATFORM == U_PF_LINUX || U_PLATFORM == U_PF_DARWIN) /* add platforms here .. */
-                 log_verbose("Skipping potentially crashing test for mismatched varargs.\n");
- #else
-                 log_verbose("Note: the next is a platform dependent test. If it crashes, add an exclusion for your platform near %s:%d\n", __FILE__, __LINE__); 
diff --git a/pkgs/os-specific/darwin/sourceRelease/versions.json b/pkgs/os-specific/darwin/sourceRelease/versions.json
index 933aa066417e..de9dff82d2cb 100644
--- a/pkgs/os-specific/darwin/sourceRelease/versions.json
+++ b/pkgs/os-specific/darwin/sourceRelease/versions.json
@@ -16,8 +16,8 @@
     "version": "88"
   },
   "ICU": {
-    "hash": "sha256-qtv+IUEjdY5I87wDEIO9cWFAh1WmnIDVIzIyyL9NTd8=",
-    "version": "76142.3.1.1"
+    "hash": "sha256-NnTaNtYDDSNe7wLr9U/raaCXGBDWHMt91HJcumY0qTQ=",
+    "version": "76142.4.7"
   },
   "IOAudioFamily": {
     "hash": "sha256-A3iiAjjP29VdjMj40tLS5Q/ni4qeh9bBpnmNzeG2pIY=",