diff --git a/include/compat/string.h b/include/compat/string.h
index f0a0711..4bf7519 100644
--- a/include/compat/string.h
+++ b/include/compat/string.h
@@ -18,9 +18,10 @@
 
 #include <sys/types.h>
 
-#if defined(__sun) || defined(__hpux)
+#if defined(__sun) || defined(_AIX) || defined(__hpux)
 /* Some functions historically defined in string.h were placed in strings.h by
- * SUS. Use the same hack as OS X and FreeBSD use to work around on Solaris and HPUX.
+ * SUS. Use the same hack as OS X and FreeBSD use to work around on AIX,
+ * Solaris, and HPUX.
  */
 #include <strings.h>
 #endif
diff --git a/libtls-standalone/include/string.h b/libtls-standalone/include/string.h
index f0a0711..4bf7519 100644
--- a/libtls-standalone/include/string.h
+++ b/libtls-standalone/include/string.h
@@ -18,9 +18,10 @@
 
 #include <sys/types.h>
 
-#if defined(__sun) || defined(__hpux)
+#if defined(__sun) || defined(_AIX) || defined(__hpux)
 /* Some functions historically defined in string.h were placed in strings.h by
- * SUS. Use the same hack as OS X and FreeBSD use to work around on Solaris and HPUX.
+ * SUS. Use the same hack as OS X and FreeBSD use to work around on AIX,
+ * Solaris, and HPUX.
  */
 #include <strings.h>
 #endif