diff --git a/pkgs/by-name/fa/fastJson/package.nix b/pkgs/by-name/li/libfastjson/package.nix
similarity index 95%
rename from pkgs/by-name/fa/fastJson/package.nix
rename to pkgs/by-name/li/libfastjson/package.nix
index 1f86fc65caab..be26d83e895f 100644
--- a/pkgs/by-name/fa/fastJson/package.nix
+++ b/pkgs/by-name/li/libfastjson/package.nix
@@ -6,7 +6,7 @@
 }:
 
 stdenv.mkDerivation (finalAttrs: {
-  pname = "fastjson";
+  pname = "libfastjson";
   version = "1.2304.0";
 
   src = fetchFromGitHub {
diff --git a/pkgs/by-name/li/liblognorm/package.nix b/pkgs/by-name/li/liblognorm/package.nix
index 9240bdb87ea3..cd59051050d5 100644
--- a/pkgs/by-name/li/liblognorm/package.nix
+++ b/pkgs/by-name/li/liblognorm/package.nix
@@ -6,7 +6,7 @@
   libestr,
   json_c,
   pcre,
-  fastJson,
+  libfastjson,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -23,7 +23,7 @@ stdenv.mkDerivation (finalAttrs: {
     libestr
     json_c
     pcre
-    fastJson
+    libfastjson
   ];
 
   configureFlags = [ "--enable-regexp" ];
diff --git a/pkgs/by-name/mm/mmdoc/package.nix b/pkgs/by-name/mm/mmdoc/package.nix
index f7945b81c88f..dd09c19978ec 100644
--- a/pkgs/by-name/mm/mmdoc/package.nix
+++ b/pkgs/by-name/mm/mmdoc/package.nix
@@ -4,7 +4,7 @@
   fetchFromGitHub,
   cmark-gfm,
   xxd,
-  fastJson,
+  libfastjson,
   libzip,
   ninja,
   meson,
@@ -31,7 +31,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   buildInputs = [
     cmark-gfm
-    fastJson
+    libfastjson
     libzip
   ];
 
diff --git a/pkgs/tools/system/rsyslog/default.nix b/pkgs/tools/system/rsyslog/default.nix
index 4820a367912c..f9e2b7668110 100644
--- a/pkgs/tools/system/rsyslog/default.nix
+++ b/pkgs/tools/system/rsyslog/default.nix
@@ -8,7 +8,7 @@
   json_c,
   zlib,
   docutils,
-  fastJson,
+  libfastjson,
   withKrb5 ? true,
   libkrb5,
   withSystemd ? lib.meta.availableOn stdenv.hostPlatform systemd,
@@ -76,7 +76,7 @@ stdenv.mkDerivation rec {
   ];
 
   buildInputs = [
-    fastJson
+    libfastjson
     libestr
     json_c
     zlib
diff --git a/pkgs/top-level/aliases.nix b/pkgs/top-level/aliases.nix
index 4b6fa9450c33..8cb2cddece59 100644
--- a/pkgs/top-level/aliases.nix
+++ b/pkgs/top-level/aliases.nix
@@ -657,6 +657,7 @@ mapAliases {
   f3d_egl = warnAlias "'f3d' now build with egl support by default, so `f3d_egl` is deprecated, consider using 'f3d' instead." f3d; # Added 2025-07-18
   fabs = throw "'fabs' has been removed due to being broken for more than a year; see RFC 180"; # Added 2026-02-05
   fast-cli = throw "'fast-cli' has been removed because it was unmaintainable in nixpkgs"; # Added 2025-11-17
+  fastJson = warnAlias "'fastJson' has been renamed to 'libfastjson'" libfastjson; # Added 2026-02-08
   fastnlo_toolkit = throw "'fastnlo_toolkit' has been renamed to/replaced by 'fastnlo-toolkit'"; # Converted to throw 2025-10-27
   faustPhysicalModeling = warnAlias "'faustPhysicalModeling' has been renamed to 'faust-physicalmodeling'" faust-physicalmodeling; # Added 2026-02-08
   faustStk = throw "'faustStk' has been renamed to/replaced by 'faustPhysicalModeling'"; # Converted to throw 2025-10-27