diff --git a/crypto/mdc2/mdc2dgst.c b/crypto/mdc2/mdc2dgst.c
index 6397a47e92dc2..37d99f48a5ebc 100644
--- a/crypto/mdc2/mdc2dgst.c
+++ b/crypto/mdc2/mdc2dgst.c
@@ -42,7 +42,7 @@ int MDC2_Update(MDC2_CTX *c, const unsigned char *in, size_t len)
 
     i = c->num;
     if (i != 0) {
-        if (i + len < MDC2_BLOCK) {
+        if (len < MDC2_BLOCK - i) {
             /* partial block */
             memcpy(&(c->data[i]), in, len);
             c->num += (int)len;