diff --git a/src/asm/lexer.c b/src/asm/lexer.c
index c928d7d6..814da5ba 100644
--- a/src/asm/lexer.c
+++ b/src/asm/lexer.c
@@ -1,6 +1,8 @@
+#define _XOPEN_SOURCE 500
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <ctype.h>
 
 #include "asm/asm.h"
diff --git a/src/asm/symbol.c b/src/asm/symbol.c
index aebe5930..0285e627 100644
--- a/src/asm/symbol.c
+++ b/src/asm/symbol.c
@@ -5,6 +5,7 @@
  *
  */
 
+#define _XOPEN_SOURCE 500
 #include <stdio.h>
 #include <string.h>
 #include <time.h>
diff --git a/src/asm/yaccprt1.y b/src/asm/yaccprt1.y
index e25e11d0..5f008f2f 100644
--- a/src/asm/yaccprt1.y
+++ b/src/asm/yaccprt1.y
@@ -1,10 +1,12 @@
 %{
+#define _XOPEN_SOURCE 500
 #include <ctype.h>
 #include <errno.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 
 #include "asm/symbol.h"
 #include "asm/asm.h"