diff --git a/src/lilv_config.h b/src/lilv_config.h
index d348a03..0dbc4d7 100644
--- a/src/lilv_config.h
+++ b/src/lilv_config.h
@@ -20,6 +20,8 @@
 
 #if !defined(LILV_NO_DEFAULT_CONFIG)
 
+#define _GNU_SOURCE
+
 // We need unistd.h to check _POSIX_VERSION
 #  ifndef LILV_NO_POSIX
 #    ifdef __has_include
@@ -33,7 +35,7 @@
 
 // POSIX.1-2001: fileno()
 #  ifndef HAVE_FILENO
-#    if defined(_POSIX_VERSION) && _POSIX_VERSION >= 200112L
+#    if defined(_POSIX_VERSION) && _POSIX_VERSION >= 200112L && !defined(__EMSCRIPTEN__)
 #      define HAVE_FILENO
 #    endif
 #  endif