diff --git a/libc/src/string.cpp b/libc/src/string.cpp
index 9c46a6c8..eabdc00a 100644
--- a/libc/src/string.cpp
+++ b/libc/src/string.cpp
@@ -1,4 +1,3 @@
-#define _LUNA_SYSTEM_ERROR_EXTENSIONS
 #include <luna/SystemError.h>
 #include <string.h>
 
@@ -7,6 +6,8 @@ extern "C"
     // All other string functions are defined in luna/CString.cpp, so the same definitions can be used by both kernel
     // and userspace.
 
+    extern "C++" const char* error_string(int);
+
     char* strerror(int errnum)
     {
         return const_cast<char*>(error_string(errnum));
diff --git a/libluna/include/luna/Result.h b/libluna/include/luna/Result.h
index 9c261e74..a902dd0b 100644
--- a/libluna/include/luna/Result.h
+++ b/libluna/include/luna/Result.h
@@ -1,5 +1,4 @@
 #pragma once
-#define _LUNA_SYSTEM_ERROR_EXTENSIONS
 #include <luna/Check.h>
 #include <luna/Move.h>
 #include <luna/Option.h>
@@ -7,6 +6,8 @@
 #include <luna/SystemError.h>
 #include <luna/Types.h>
 
+extern const char* error_string(int error);
+
 struct Error
 {
     Error(int err)
diff --git a/libluna/include/luna/SystemError.h b/libluna/include/luna/SystemError.h
index 2a8962f4..869f7a7f 100644
--- a/libluna/include/luna/SystemError.h
+++ b/libluna/include/luna/SystemError.h
@@ -53,14 +53,3 @@
 #define EISCONN 106     // Transport endpoint is already connected
 #define ETIMEDOUT 110   // Connection timed out
 #define EALREADY 114    // Operation already in progress
-
-#if defined(IN_MOON) || defined(USE_FREESTANDING) || defined(_LUNA_SYSTEM_ERROR_EXTENSIONS) || defined(_LUNA_SOURCE)
-// This one is Luna-specific.
-#define EFIXME 342 // Functionality not yet implemented
-
-#ifndef _LUNA_SOURCE
-const char* error_string(int error);
-const char* error_name(int error);
-#endif
-
-#endif
diff --git a/libluna/src/SystemError.cpp b/libluna/src/SystemError.cpp
index 5484a76f..9b7bf473 100644
--- a/libluna/src/SystemError.cpp
+++ b/libluna/src/SystemError.cpp
@@ -1,4 +1,3 @@
-#define _LUNA_SYSTEM_ERROR_EXTENSIONS
 #include <luna/SystemError.h>
 
 const char* error_string(int error)
@@ -57,7 +56,6 @@ const char* error_string(int error)
     case EISCONN: return "Transport endpoint is already connected";
     case ETIMEDOUT: return "Connection timed out";
     case EALREADY: return "Operation already in progress";
-    case EFIXME: return "Functionality not yet implemented";
     default: return "Unknown error";
     }
 }