diff --git a/tests/logit_difference_validator.inc b/tests/logit_difference_validator.inc
index acde72a..9ff0591 100644
--- a/tests/logit_difference_validator.inc
+++ b/tests/logit_difference_validator.inc
@@ -1,6 +1,7 @@
 #ifndef LOGIT_DIFFERENCE_VALIDATOR_INC
 #define LOGIT_DIFFERENCE_VALIDATOR_INC
 
+#include <string.h>
 #include <math.h>
 
 #include <rwkv.h>