diff --git a/config/CMakeLists.txt b/config/CMakeLists.txt
index 65b898d..9713799 100644
--- a/config/CMakeLists.txt
+++ b/config/CMakeLists.txt
@@ -32,6 +32,9 @@ check_function_exists(canonicalize_file_name HAVE_CANONICALIZE_FILE_NAME)
 check_function_exists(dcgettext HAVE_DCGETTEXT)
 check_function_exists(iconv HAVE_ICONV)
 
+include(CheckSymbolExists)
+check_symbol_exists(canonicalize_file_name stdlib.h HAVE_CANONICALIZE_FILE_NAME_DECL)
+
 include(CheckLibraryExists)
 check_library_exists(m pow "" HAVE_LIBM)
 check_library_exists(dl dlopen "" HAVE_LIBDL)
diff --git a/config/config.h.in b/config/config.h.in
index 9c35cce..8d19151 100644
--- a/config/config.h.in
+++ b/config/config.h.in
@@ -38,6 +38,9 @@
 /* Define to 1 if you have the `canonicalize_file_name' function. */
 #cmakedefine HAVE_CANONICALIZE_FILE_NAME @HAVE_CANONICALIZE_FILE_NAME@
 
+/* Define to 1 if canonicalize_file_name is declared in system header files. */
+#cmakedefine HAVE_CANONICALIZE_FILE_NAME_DECL @HAVE_CANONICALIZE_FILE_NAME_DECL@
+
 /* Define to 1 if you have the Mac OS X function CFLocaleCopyCurrent in the
    CoreFoundation framework. */
 #undef HAVE_CFLOCALECOPYCURRENT
@@ -121,9 +124,6 @@
 /* Define to the sub-directory where libtool stores uninstalled libraries. */
 //#undef LT_OBJDIR
 
-/* Define if canonicalize_file_name is not declared in system header files. */
-#undef NEED_DECLARATION_CANONICALIZE_FILE_NAME
-
 /* Name of package */
 #define PACKAGE "@PACKAGE@"
 
diff --git a/src/lrealpath.c b/src/lrealpath.c
index e75184e..2d9780c 100644
--- a/src/lrealpath.c
+++ b/src/lrealpath.c
@@ -53,7 +53,7 @@ components will be simplified.  The returned value will be allocated using
 
 /* On GNU libc systems the declaration is only visible with _GNU_SOURCE.  */
 #if defined(HAVE_CANONICALIZE_FILE_NAME) \
-    && defined(NEED_DECLARATION_CANONICALIZE_FILE_NAME)
+    && ! defined(HAVE_CANONICALIZE_FILE_NAME_DECL)
 extern char *canonicalize_file_name (const char *);
 #endif