diff --git a/multimedia/gst1-libav/Makefile b/multimedia/gst1-libav/Makefile
index 3137e000e..36a25293a 100644
--- a/multimedia/gst1-libav/Makefile
+++ b/multimedia/gst1-libav/Makefile
@@ -185,7 +185,7 @@ CONFIGURE_ARGS += \
 	--disable-yasm"
 
 # XXX: trick to force use of embedded Libav headers
-TARGET_CFLAGS += $(TARGET_CPPFLAGS)
+TARGET_CFLAGS += $(TARGET_CPPFLAGS) -D_GNU_SOURCE
 TARGET_CPPFLAGS :=
 
 TARGET_LDFLAGS += $(FPIC)