diff --git a/tests/test.c b/tests/test.c
index c6f9dbe..dd5a315 100644
--- a/tests/test.c
+++ b/tests/test.c
@@ -202,15 +202,21 @@ static int json_to_url(cJSON *json, URL *url)
         url->fragment.len--;
     }
 
-    char tmp[8];
-    if (port.len >= (int) sizeof(tmp)) {
-        test_printf(" JSON object's port field is longer than expected\n");
-        return -1;
-    }
-    memcpy(tmp, port.ptr, port.len);
-    tmp[port.len] = 0;
+    if (port.len == 0) {
+        url->no_port = 1;
+        url->port = 0;
+    } else {
+        char tmp[8];
+        if (port.len >= (int) sizeof(tmp)) {
+            test_printf(" JSON object's port field is longer than expected\n");
+            return -1;
+        }
+        memcpy(tmp, port.ptr, port.len);
+        tmp[port.len] = 0;
 
-    url->port = atoi(tmp);
+        url->no_port = 0;
+        url->port = atoi(tmp);
+    }
     return 0;
 }
 
@@ -269,6 +275,20 @@ static int compare_urls(URL parsed, URL expected)
         ok = false;
     }
 
+    if (parsed.no_port != expected.no_port) {
+        if (ok) test_printf("\n");
+        if (parsed.no_port) {
+            test_printf("  port mismatch\n");
+            test_printf("    parsed   (empty)\n");
+            test_printf("    expected [%d]\n", expected.port);
+        } else {
+            test_printf("  port mismatch\n");
+            test_printf("    parsed   [%d]\n", parsed.port);
+            test_printf("    expected (empty)\n");
+        }
+        ok = false;
+    }
+
     if (parsed.port != expected.port) {
         if (ok) test_printf("\n");
         test_printf("  port mismatch\n");
diff --git a/url.c b/url.c
index 73d01f8..31f4887 100644
--- a/url.c
+++ b/url.c
@@ -580,25 +580,26 @@ int url_parse(char *src, int len, int *pcur, URL *out, int flags)
         out->no_port = 1;
         out->port    = 0;
         if (cur < len && src[cur] == ':') {
-
-            // The WHATWG standard forbids port numbers with the
-            // "file" protocol.
-            if ((flags & URL_FLAG_RFC3986) == 0) {
-                if (streqcase(out->scheme, S("file")))
-                    return -1;
-            }
-
             cur++; // Consume the ':'
-            out->no_port = 0;
 
-            while (cur < len && is_digit(src[cur])) {
+            if (cur < len && is_digit(src[cur])) {
 
-                int n = src[cur] - '0';
-                cur++;
+                // The WHATWG standard forbids port numbers with the
+                // "file" protocol.
+                if ((flags & URL_FLAG_RFC3986) == 0) {
+                    if (streqcase(out->scheme, S("file")))
+                        return -1;
+                }
 
-                if (out->port > (UINT16_MAX - n) / 10)
-                    return -1; // Overflow
-                out->port = out->port * 10 + n;
+                out->no_port = 0;
+                do {
+                    int n = src[cur] - '0';
+                    cur++;
+
+                    if (out->port > (UINT16_MAX - n) / 10)
+                        return -1; // Overflow
+                    out->port = out->port * 10 + n;
+                } while (cur < len && is_digit(src[cur]));
             }
         }