diff --git a/Makefile.am b/Makefile.am
index 24611c9e..9b107b71 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -101,7 +101,7 @@ lib_LTLIBRARIES += src/libespeak-ng.la
 
 src_libespeak_ng_la_LDFLAGS = -version-info $(SHARED_VERSION) -lpthread -lm
 src_libespeak_ng_la_CFLAGS = -Isrc/include \
-	-fPIC -fvisibility=hidden -D _BSD_SOURCE -D _POSIX_C_SOURCE=200112L \
+	-fPIC -fvisibility=hidden -D _BSD_SOURCE -D_DEFAULT_SOURCE -D _POSIX_C_SOURCE=200112L \
 	-pedantic -fno-exceptions -D PATH_ESPEAK_DATA=\"$(DATADIR)\"
 src_libespeak_ng_la_SOURCES = \
 	src/libespeak-ng/compiledata.c \