diff --git a/src/building_action.c b/src/building_action.c
index a11ccbfd4..a0656773e 100644
--- a/src/building_action.c
+++ b/src/building_action.c
@@ -25,6 +25,7 @@ without prior permission by the authors of Eressea.
 
 #include <assert.h>
 #include <stdlib.h>
+#include <string.h>
 
 typedef struct building_action {
     struct building *b;