diff --git a/contrib/credential/wincred/git-credential-wincred.c b/contrib/credential/wincred/git-credential-wincred.c
index 73c2b9b72ab53e..22eb27ca31dea0 100644
--- a/contrib/credential/wincred/git-credential-wincred.c
+++ b/contrib/credential/wincred/git-credential-wincred.c
@@ -121,10 +121,10 @@ static int match_part_last(LPCWSTR *ptarget, LPCWSTR want, LPCWSTR delim)
 
 static int match_cred_password(const CREDENTIALW *cred) {
 	int ret;
-	WCHAR *cred_password = xmalloc(cred->CredentialBlobSize);
-	wcsncpy_s(cred_password, cred->CredentialBlobSize,
-		(LPCWSTR)cred->CredentialBlob,
-		cred->CredentialBlobSize / sizeof(WCHAR));
+	size_t wlen = cred->CredentialBlobSize / sizeof(WCHAR);
+	WCHAR *cred_password = xmalloc((wlen + 1) * sizeof(WCHAR));
+	wcsncpy_s(cred_password, wlen + 1,
+		(LPCWSTR)cred->CredentialBlob, wlen);
 	ret = !wcscmp(cred_password, password);
 	free(cred_password);
 	return ret;
@@ -208,8 +208,8 @@ static void store_credential(void)
 
 	if (oauth_refresh_token) {
 		wlen = _scwprintf(L"%s\r\noauth_refresh_token=%s", password, oauth_refresh_token);
-		secret = xmalloc(sizeof(WCHAR) * wlen);
-		_snwprintf_s(secret, sizeof(WCHAR) * wlen, wlen, L"%s\r\noauth_refresh_token=%s", password, oauth_refresh_token);
+		secret = xmalloc((wlen + 1) * sizeof(WCHAR));
+		_snwprintf_s(secret, wlen + 1, wlen, L"%s\r\noauth_refresh_token=%s", password, oauth_refresh_token);
 	} else {
 		secret = _wcsdup(password);
 	}