diff --git a/lib/curlx/strerr.c b/lib/curlx/strerr.c
index b53173c578..1d1e40d164 100644
--- a/lib/curlx/strerr.c
+++ b/lib/curlx/strerr.c
@@ -268,7 +268,7 @@ const char *curlx_strerror(int err, char *buf, size_t buflen)
      !get_winsock_error(err, buf, buflen) &&
 #endif
      !curlx_get_winapi_error((DWORD)err, buf, buflen))
-    SNPRINTF(buf, buflen, "Unknown error %d (%#x)", err, err);
+    SNPRINTF(buf, buflen, "Unknown error %d (%#x)", err, (unsigned int)err);
 #else /* !_WIN32 */
 
 #if defined(HAVE_STRERROR_R) && defined(HAVE_POSIX_STRERROR_R)
diff --git a/lib/vtls/schannel.c b/lib/vtls/schannel.c
index 05bd6a5194..fb5ff0e9d8 100644
--- a/lib/vtls/schannel.c
+++ b/lib/vtls/schannel.c
@@ -1670,7 +1670,7 @@ static CURLcode schannel_connect_step3(struct Curl_cfilter *cf,
 
     traverse_cert_store(ccert_context, cert_counter_callback, &certs_count);
     if(certs_count > MAX_ALLOWED_CERT_AMOUNT) {
-      failf(data, "%d certificates is more than allowed (%u)",
+      failf(data, "%d certificates is more than allowed (%d)",
             certs_count, MAX_ALLOWED_CERT_AMOUNT);
       CertFreeCertificateContext(ccert_context);
       return CURLE_SSL_CONNECT_ERROR;
diff --git a/lib/vtls/schannel_verify.c b/lib/vtls/schannel_verify.c
index 3e0130c8e9..9be6fe311c 100644
--- a/lib/vtls/schannel_verify.c
+++ b/lib/vtls/schannel_verify.c
@@ -290,7 +290,7 @@ static CURLcode add_certs_file_to_store(HCERTSTORE trust_store,
   }
 
   if(file_size.QuadPart > MAX_CAFILE_SIZE) {
-    failf(data, "schannel: CA file exceeds max size of %u bytes",
+    failf(data, "schannel: CA file exceeds max size of %d bytes",
           MAX_CAFILE_SIZE);
     result = CURLE_SSL_CACERT_BADFILE;
     goto cleanup;