diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index 59039bea4ff..8267988ad9c 100644
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -721,6 +721,10 @@ bool ifname_valid_full(const char *p, IfnameValidFlags flags) {
         if (isempty(p))
                 return false;
 
+        /* A valid ifindex? If so, it's valid iff IFNAME_VALID_NUMERIC is set */
+        if (parse_ifindex(p) >= 0)
+                return flags & IFNAME_VALID_NUMERIC;
+
         if (flags & IFNAME_VALID_ALTERNATIVE) {
                 if (strlen(p) >= ALTIFNAMSIZ)
                         return false;
@@ -745,14 +749,10 @@ bool ifname_valid_full(const char *p, IfnameValidFlags flags) {
                 numeric = numeric && (*t >= '0' && *t <= '9');
         }
 
-        if (numeric) {
-                if (!(flags & IFNAME_VALID_NUMERIC))
-                        return false;
-
-                /* Verify that the number is well-formatted and in range. */
-                if (parse_ifindex(p) < 0)
-                        return false;
-        }
+        /* It's fully numeric but didn't parse as valid ifindex above? if so, it must be too large or zero or
+         * so, let's refuse that. */
+        if (numeric)
+                return false;
 
         return true;
 }
diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
index b741a90be7b..2c98283cd34 100644
--- a/src/basic/socket-util.h
+++ b/src/basic/socket-util.h
@@ -133,9 +133,9 @@ int ip_tos_to_string_alloc(int i, char **s);
 int ip_tos_from_string(const char *s);
 
 typedef enum {
-      IFNAME_VALID_ALTERNATIVE = 1 << 0,
-      IFNAME_VALID_NUMERIC     = 1 << 1,
-      _IFNAME_VALID_ALL        = IFNAME_VALID_ALTERNATIVE | IFNAME_VALID_NUMERIC,
+        IFNAME_VALID_ALTERNATIVE = 1 << 0,
+        IFNAME_VALID_NUMERIC     = 1 << 1,
+        _IFNAME_VALID_ALL        = IFNAME_VALID_ALTERNATIVE | IFNAME_VALID_NUMERIC,
 } IfnameValidFlags;
 bool ifname_valid_full(const char *p, IfnameValidFlags flags);
 static inline bool ifname_valid(const char *p) {