diff --git a/src/esi/Assign.cc b/src/esi/Assign.cc

index eb68e84..08ce5a5 100644

--- a/src/esi/Assign.cc

+++ b/src/esi/Assign.cc

@@ -41,6 +41,7 @@

 #include "esi/Assign.h"

 #include "esi/Context.h"

 #include "esi/Sequence.h"

+#include "HttpReply.h"

 ESIAssign::~ESIAssign()

 {

diff --git a/src/esi/Esi.cc b/src/esi/Esi.cc

index 60c2344..ef236a9 100644

--- a/src/esi/Esi.cc

+++ b/src/esi/Esi.cc

@@ -1007,7 +1006,7 @@ ESIContext::start(const char *el, const char **attr, size_t attrCount)

     ESIElement::Pointer element;

     int specifiedattcount = attrCount * 2;

     char *position;

-    assert (ellen < sizeof (localbuf)); /* prevent unexpected overruns. */

+    Must(ellen < sizeof(localbuf)); /* prevent unexpected overruns. */

     debugs(86, 5, "ESIContext::Start: element '" << el << "' with " << specifiedattcount << " tags");

@@ -1021,15 +1020,17 @@ ESIContext::start(const char *el, const char **attr, size_t attrCount)

         /* Spit out elements we aren't interested in */

         localbuf[0] = '<';

         localbuf[1] = '\0';

-        assert (xstrncpy (&localbuf[1], el, sizeof(localbuf) - 2));

+        xstrncpy(&localbuf[1], el, sizeof(localbuf) - 2);

         position = localbuf + strlen (localbuf);

         for (i = 0; i < specifiedattcount && attr[i]; i += 2) {

+            Must(static_cast<size_t>(position - localbuf) < sizeof(localbuf) - 1);

             *position = ' ';

             ++position;

             /* TODO: handle thisNode gracefully */

-            assert (xstrncpy (position, attr[i], sizeof(localbuf) + (position - localbuf)));

+            xstrncpy(position, attr[i], sizeof(localbuf) - (position - localbuf));

             position += strlen (position);

+            Must(static_cast<size_t>(position - localbuf) < sizeof(localbuf) - 2);

             *position = '=';

             ++position;

             *position = '\"';

@@ -1038,18 +1039,21 @@ ESIContext::start(const char *el, const char **attr, size_t attrCount)

             char ch;

             while ((ch = *chPtr++) != '\0') {

                 if (ch == '\"') {

-                    assert( xstrncpy(position, """, sizeof(localbuf) + (position-localbuf)) );

+                    Must(static_cast<size_t>(position - localbuf) < sizeof(localbuf) - 6);

+                    xstrncpy(position, """, sizeof(localbuf) - (position-localbuf));

                     position += 6;

                 } else {

+                    Must(static_cast<size_t>(position - localbuf) < sizeof(localbuf) - 1);

                     *position = ch;

                     ++position;

                 }

             }

-            position += strlen (position);

+            Must(static_cast<size_t>(position - localbuf) < sizeof(localbuf) - 1);

             *position = '\"';

             ++position;

         }

+        Must(static_cast<size_t>(position - localbuf) < sizeof(localbuf) - 2);

         *position = '>';

         ++position;

         *position = '\0';

@@ -1135,11 +1139,11 @@ ESIContext::end(const char *el)

     switch (ESIElement::IdentifyElement (el)) {

     case ESIElement::ESI_ELEMENT_NONE:

-        assert (ellen < sizeof (localbuf)); /* prevent unexpected overruns. */

+        Must(ellen < sizeof(localbuf) - 3); /* prevent unexpected overruns. */

         /* Add elements we aren't interested in */

         localbuf[0] = '<';

         localbuf[1] = '/';

-        assert (xstrncpy (&localbuf[2], el, sizeof(localbuf) - 3));

+        xstrncpy(&localbuf[2], el, sizeof(localbuf) - 3);

         position = localbuf + strlen (localbuf);

         *position = '>';

         ++position;