diff --git a/src/core/pbuf.c b/src/core/pbuf.c
index 73e4e6f4..51ae6f5a 100644
--- a/src/core/pbuf.c
+++ b/src/core/pbuf.c
@@ -599,7 +599,7 @@ pbuf_free(struct pbuf *p)
     /* all pbufs in a chain are referenced at least once */
     LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
     /* decrease reference count (number of pointers to pbuf) */
-    ref = p->ref--;
+    ref = --(p->ref);
     SYS_ARCH_UNPROTECT(old_level);
     /* this pbuf is no longer referenced to? */
     if (ref == 0) {