diff --git a/pkgs/by-name/am/amber-lang/fix_gnused_detection.patch b/pkgs/by-name/am/amber-lang/fix_gnused_detection.patch
deleted file mode 100644
index a4d2e99ea729..000000000000
--- a/pkgs/by-name/am/amber-lang/fix_gnused_detection.patch
+++ /dev/null
@@ -1,29 +0,0 @@
-From cae2ad70d6202bc97623be8c7c123ee2736a4644 Mon Sep 17 00:00:00 2001
-From: aleksana <me@aleksana.moe>
-Date: Sun, 9 Mar 2025 21:19:27 +0800
-Subject: [PATCH] replace_regex: remove bash word boundary when detecting
- gnused
-
-Bash linked against C libraries other than GLibc may not support GNU
-extensions of POSIX Extended Regular Regex. For example,
-
-> re='\bx'; [[ 'x' =~ $re ]] && echo "1"
-
-does not output the same result on Linux/GLibc and macOS.
----
- src/std/text.ab | 2 +-
- 1 file changed, 1 insertion(+), 1 deletion(-)
-
-diff --git a/src/std/text.ab b/src/std/text.ab
-index fe071e33..82449a02 100644
---- a/src/std/text.ab
-+++ b/src/std/text.ab
-@@ -19,7 +19,7 @@ pub fun replace_regex(source: Text, search: Text, replace: Text, extended: Bool
-             // GNU sed versions 4.0 through 4.2 support extended regex syntax,
-             // but only via the "-r" option; use that if the version information
-             // contains "GNU sed".
--            $ re='\bCopyright\b.+\bFree Software Foundation\b'; [[ \$(sed --version 2>/dev/null) =~ \$re ]] $
-+            $ re='Copyright.+Free Software Foundation'; [[ \$(sed --version 2>/dev/null) =~ \$re ]] $
-             let flag = status == 0 then "-r" else "-E"
-             return $ echo "{source}" | sed "{flag}" -e "s/{search}/{replace}/g" $
-         } else {
diff --git a/pkgs/by-name/am/amber-lang/fix_word_boundaries.patch b/pkgs/by-name/am/amber-lang/fix_word_boundaries.patch
new file mode 100644
index 000000000000..ec73631eccae
--- /dev/null
+++ b/pkgs/by-name/am/amber-lang/fix_word_boundaries.patch
@@ -0,0 +1,38 @@
+From efdbecaf721ccb217ece34a5105eaac68e27aa51 Mon Sep 17 00:00:00 2001
+From: Max Karou <maxkarou@protonmail.com>
+Date: Sun, 4 Jan 2026 01:47:51 +0100
+Subject: [PATCH] sed_version: remove word boundary assertions
+
+Word boundary assertions (\b) are GNU regex extensions that may fail
+on systems using non-glibc C libraries (e.g., musl, macOS).
+
+This was previously fixed in replace_regex() via NixOS/nixpkgs#388412,
+which was subsequently upstreamed in amber-lang/amber#686.
+
+Changes in amber-lang/amber#717 reintroduced the same portability issue.
+---
+ src/std/text.ab | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/src/std/text.ab b/src/std/text.ab
+index 5f2d935..a5dac3f 100644
+--- a/src/std/text.ab
++++ b/src/std/text.ab
+@@ -51,12 +51,12 @@ const SED_VERSION_BUSYBOX = 2
+ fun sed_version(): Int {
+     // We can't match against a word "GNU" because
+     // alpine's busybox sed returns "This is not GNU sed version"
+-    trust $ re='\bCopyright\b.+\bFree Software Foundation\b'; [[ \$(sed --version 2>/dev/null) =~ \$re ]] $
++    trust $ re='Copyright.+Free Software Foundation'; [[ \$(sed --version 2>/dev/null) =~ \$re ]] $
+     if status == 0 {
+         return SED_VERSION_GNU
+     }
+     // On BSD single `sed` waits for stdin. We must use `sed --help` to avoid this.
+-    trust $ re='\bBusyBox\b'; [[ \$(sed --help 2>&1) =~ \$re ]] $
++    trust $ re='BusyBox'; [[ \$(sed --help 2>&1) =~ \$re ]] $
+     if status == 0 {
+         return SED_VERSION_BUSYBOX
+     }
+-- 
+2.51.2
+
diff --git a/pkgs/by-name/am/amber-lang/package.nix b/pkgs/by-name/am/amber-lang/package.nix
index e3180bf19415..a704fbd47fa1 100644
--- a/pkgs/by-name/am/amber-lang/package.nix
+++ b/pkgs/by-name/am/amber-lang/package.nix
@@ -15,21 +15,22 @@
 
 rustPlatform.buildRustPackage rec {
   pname = "amber-lang";
-  version = "0.4.0-alpha";
+  version = "0.5.1-alpha";
 
   src = fetchFromGitHub {
     owner = "amber-lang";
     repo = "amber";
     tag = version;
-    hash = "sha256-N9G/2G8+vrpr1/K7XLwgW+X2oAyAaz4qvN+EbLOCU1Q=";
+    hash = "sha256-v1uJe3vVGKXaZcQzdoYzu/bJKMQnS4IYET4QLPW+J8Y=";
   };
 
   patches = [
-    # https://github.com/amber-lang/amber/pull/686
-    ./fix_gnused_detection.patch
+    # Upstreamed in #995, can be removed in >= 0.5.2
+    # github.com/amber-lang/amber/pull/995
+    ./fix_word_boundaries.patch
   ];
 
-  cargoHash = "sha256-e5+L7Qgd6hyqT1Pb9X7bVtRr+xm428Z5J4hhsYNnGtU=";
+  cargoHash = "sha256-aXcxlmmDYLFbyRJYyGE1gbQMbdysHx4iWXsrUj10Eco=";
 
   preConfigure = ''
     substituteInPlace src/compiler.rs \