diff --git a/admin/alloc-colors.c b/admin/alloc-colors.c
index 4db447332ba..b78dd42b7e6 100644
--- a/admin/alloc-colors.c
+++ b/admin/alloc-colors.c
@@ -23,6 +23,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <stdlib.h>
 #include <stdarg.h>
 #include <unistd.h>
+#include <string.h>
 
 void
 fatal (const char *fmt, ...)