diff --git a/src/crypto/rfc3961/krb5_locl.h b/src/crypto/rfc3961/krb5_locl.h
index e575084fcf..04292eefaf 100644
--- a/src/crypto/rfc3961/krb5_locl.h
+++ b/src/crypto/rfc3961/krb5_locl.h
@@ -66,6 +66,10 @@
 
 #define ALLOC(X, N) (X) = calloc((N), sizeof(*(X)))
 
+#ifndef max
+#define max(a,b) (((a)>(b))?(a):(b))
+#endif
+
 #ifndef O_BINARY
 #define O_BINARY 0
 #endif