diff --git a/src/ip.h b/src/ip.h
index a1cf83f..d636148 100644
--- a/src/ip.h
+++ b/src/ip.h
@@ -29,15 +29,15 @@ ip_read16(const uint8_t *src)
 static inline uint8_t
 ip_get_version(const uint8_t *data)
 {
+    if (size < 20)
+        return 0;
+
     return data[0] >> 4;
 }
 
 static inline int
 ip_is_valid(const uint8_t *data, int size)
 {
-    if (size < 20)
-        return 0;
-
     switch (ip_get_version(data)) {
         case 4: return size == ip_read16(&data[2]);
         case 6: return size == ip_read16(&data[4]) + 40;
@@ -49,9 +49,6 @@ ip_is_valid(const uint8_t *data, int size)
 static inline int
 ip_get_common(struct ip_common *ic, const uint8_t *data, int size)
 {
-    if (size < 20)
-        return 1;
-
     switch (ip_get_version(data)) {
     case 4:
         ic->tc = data[1];