diff --git a/Makefile b/Makefile
index cd4db59..dd861d9 100644
--- a/Makefile
+++ b/Makefile
@@ -156,6 +156,7 @@ SYMBOLS = -DUNITY_FIXTURE_NO_EXTRAS
 SYMBOLS += -DUNITY_INCLUDE_DOUBLE
 SYMBOLS += -DUNITY_DOUBLE_PRECISION=1e-12
 SYMBOLS += -DUNITY_INCLUDE_CONFIG_H
+SYMBOLS += -D_POSIX_C_SOURCE=200809
 
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 # Astyle