diff --git a/src/string.c b/src/string.c
index 6268d001..6be7c2a6 100644
--- a/src/string.c
+++ b/src/string.c
@@ -21,6 +21,7 @@
  * MA 02111-1307, USA.
  */
 
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>