diff --git a/tests/api/test_rsa.c b/tests/api/test_rsa.c
index 05fdd298bb..6179e76f3b 100644
--- a/tests/api/test_rsa.c
+++ b/tests/api/test_rsa.c
@@ -1159,6 +1159,7 @@ int test_wc_RsaKeyToDer_SizeOverflow(void)
 {
     EXPECT_DECLS;
 #if !defined(NO_RSA) && defined(USE_INTEGER_HEAP_MATH) && \
+    !defined(USE_FAST_MATH) && \
     defined(WOLFSSL_ASN_TEMPLATE) && defined(WOLFSSL_PUBLIC_MP) && \
     (defined(WOLFSSL_KEY_GEN) || defined(WOLFSSL_KEY_TO_DER))
     RsaKey    key;