diff --git a/lib/prefix.c b/lib/prefix.c
index 1806ac4..c692203 100644
--- a/lib/prefix.c
+++ b/lib/prefix.c
@@ -199,7 +199,10 @@
 {
   struct prefix_ipv4 *p;
 
-  p = XCALLOC (MTYPE_PREFIX_IPV4, sizeof *p);
+  /* Call prefix_new to allocate a full-size struct prefix to avoid problems
+     where the struct prefix_ipv4 is cast to struct prefix and unallocated
+     bytes were being referenced (e.g. in structure assignments). */
+  p = (struct prefix_ipv4 *)prefix_new();
   p->family = AF_INET;
   return p;
 }
@@ -208,7 +211,7 @@
 void
 prefix_ipv4_free (struct prefix_ipv4 *p)
 {
-  XFREE (MTYPE_PREFIX_IPV4, p);
+  prefix_free((struct prefix *)p);
 }
 
 /* When string format is invalid return 0. */
@@ -348,7 +351,9 @@
 {
   struct prefix_ipv6 *p;
 
-  p = XCALLOC (MTYPE_PREFIX_IPV6, sizeof (struct prefix_ipv6));
+  /* Allocate a full-size struct prefix to avoid problems with structure
+     size mismatches. */
+  p = (struct prefix_ipv6 *)prefix_new();
   p->family = AF_INET6;
   return p;
 }
@@ -357,7 +362,7 @@
 void
 prefix_ipv6_free (struct prefix_ipv6 *p)
 {
-  XFREE (MTYPE_PREFIX_IPV6, p);
+  prefix_free((struct prefix *)p);
 }
 
 /* If given string is valid return pin6 else return NULL */