diff --git a/tests/api.c b/tests/api.c
index 7cc6edebf..45b44f3f2 100644
--- a/tests/api.c
+++ b/tests/api.c
@@ -16662,10 +16662,8 @@ static void test_wc_PemPubKeyToDer(void)
 
     printf(testingFmt, "wc_PemPubKeyToDer()");
 
-#if 0 /* NULL filename causes valgrind failure */
     ret = wc_PemPubKeyToDer(NULL, cert_der, (int)cert_dersz);
-    AssertIntGE(ret, BUFFER_E);
-#endif
+    AssertIntGE(ret, BAD_FUNC_ARG);
 
     if (cert_der) {
         ret = wc_PemPubKeyToDer(key, cert_der, (int)cert_dersz);
@@ -19851,7 +19849,7 @@ static void test_wolfSSL_SESSION(void)
 #ifdef HAVE_SESSION_TICKET
     /* Test set/get session ticket */
     {
-        char ticket[] = "This is a session ticket";
+        const char* ticket = "This is a session ticket";
         char buf[64] = {0};
         word32 bufSz = (word32)sizeof(buf);
 
@@ -21288,7 +21286,7 @@ static void test_wc_SetIssueBuffer(void)
 {
 #if !defined(NO_ASN) && !defined(NO_FILESYSTEM) && defined(OPENSSL_EXTRA) && \
     defined(WOLFSSL_CERT_GEN) && defined(WOLFSSL_CERT_EXT)
-    char joiCertFile[] = "./certs/test/cert-ext-joi.pem";
+    const char* joiCertFile = "./certs/test/cert-ext-joi.pem";
     WOLFSSL_X509* x509;
     int peerCertSz;
     const byte* peerCertBuf;
diff --git a/wolfcrypt/src/asn.c b/wolfcrypt/src/asn.c
index db37644de..2354a6142 100644
--- a/wolfcrypt/src/asn.c
+++ b/wolfcrypt/src/asn.c
@@ -9252,15 +9252,22 @@ int wc_PemCertToDer(const char* fileName, unsigned char* derBuf, int derSz)
     int    dynamic = 0;
     int    ret     = 0;
     long   sz      = 0;
-    XFILE  file    = XFOPEN(fileName, "rb");
+    XFILE  file;
     DerBuffer* converted = NULL;
 
     WOLFSSL_ENTER("wc_PemCertToDer");
 
-    if (file == XBADFILE) {
-        ret = BUFFER_E;
+    if (fileName == NULL) {
+        ret = BAD_FUNC_ARG;
     }
     else {
+        file = XFOPEN(fileName, "rb");
+        if (file == XBADFILE) {
+            ret = BUFFER_E;
+        }
+    }
+
+    if (ret == 0) {
         if(XFSEEK(file, 0, XSEEK_END) != 0)
             ret = BUFFER_E;
         sz = XFTELL(file);
@@ -9326,15 +9333,22 @@ int wc_PemPubKeyToDer(const char* fileName,
     int    dynamic = 0;
     int    ret     = 0;
     long   sz      = 0;
-    XFILE  file    = XFOPEN(fileName, "rb");
+    XFILE  file;
     DerBuffer* converted = NULL;
 
     WOLFSSL_ENTER("wc_PemPubKeyToDer");
 
-    if (file == XBADFILE) {
-        ret = BUFFER_E;
+    if (fileName == NULL) {
+        ret = BAD_FUNC_ARG;
     }
     else {
+        file = XFOPEN(fileName, "rb");
+        if (file == XBADFILE) {
+            ret = BUFFER_E;
+        }
+    }
+
+    if (ret == 0) {
         if(XFSEEK(file, 0, XSEEK_END) != 0)
             ret = BUFFER_E;
         sz = XFTELL(file);