diff --git a/Meta/Lagom/CMakeLists.txt b/Meta/Lagom/CMakeLists.txt
index 9dfe03e4d3..ac6db3051d 100644
--- a/Meta/Lagom/CMakeLists.txt
+++ b/Meta/Lagom/CMakeLists.txt
@@ -482,10 +482,9 @@ if (BUILD_LAGOM)
     )
 
     # Regex
-    file(GLOB LIBREGEX_LIBC_SOURCES "../../Userland/Libraries/LibRegex/C/Regex.cpp")
     file(GLOB LIBREGEX_SOURCES CONFIGURE_DEPENDS "../../Userland/Libraries/LibRegex/*.cpp")
     lagom_lib(Regex regex
-        SOURCES ${LIBREGEX_SOURCES} ${LIBREGEX_LIBC_SOURCES}
+        SOURCES ${LIBREGEX_SOURCES}
         LIBS LibUnicode
     )
 
diff --git a/Userland/Libraries/LibRegex/C/Regex.cpp b/Userland/Libraries/LibRegex/C/Regex.cpp
index 28d93d5da6..b9a76394cc 100644
--- a/Userland/Libraries/LibRegex/C/Regex.cpp
+++ b/Userland/Libraries/LibRegex/C/Regex.cpp
@@ -6,19 +6,17 @@
 
 #include <AK/String.h>
 #include <AK/StringBuilder.h>
+#include <AK/Variant.h>
 #include <LibRegex/Regex.h>
 #include <ctype.h>
+#include <regex.h>
 #include <stdio.h>
 #include <string.h>
 
-#ifdef __serenity__
-#    include <regex.h>
-#else
-#    include <LibC/regex.h>
+#ifndef AK_OS_SERENITY
+#    error "This file is intended for use on Serenity only to implement POSIX regex.h"
 #endif
 
-#include <AK/Variant.h>
-
 struct internal_regex_t {
     u8 cflags;
     u8 eflags;