diff --git a/CMakeLists.txt b/CMakeLists.txt
index a8147575b..192643a64 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -610,6 +610,7 @@ SET(PCRE2_HEADERS ${PROJECT_BINARY_DIR}/pcre2.h)
 SET(PCRE2_SOURCES
   src/pcre2_auto_possess.c
   ${PROJECT_BINARY_DIR}/pcre2_chartables.c
+  src/pcre2_chkdint.c
   src/pcre2_compile.c
   src/pcre2_config.c
   src/pcre2_context.c
diff --git a/Makefile.am b/Makefile.am
index a37910da1..db7d5563d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -353,6 +353,7 @@ NODIST_SOURCES = src/pcre2_chartables.c
 
 COMMON_SOURCES = \
   src/pcre2_auto_possess.c \
+  src/pcre2_chkdint.c \
   src/pcre2_compile.c \
   src/pcre2_config.c \
   src/pcre2_context.c \
diff --git a/configure.ac b/configure.ac
index 0e462b30d..fe7d93b22 100644
--- a/configure.ac
+++ b/configure.ac
@@ -638,6 +638,8 @@ fi
 if test "$enable_debug" = "yes"; then
   AC_DEFINE([PCRE2_DEBUG], [], [
     Define to any value to include debugging code.])
+else
+  CFLAGS="$CFLAGS -DNDEBUG"
 fi
 
 if test "$enable_percent_zt" = "no"; then
diff --git a/src/pcre2_chkdint.c b/src/pcre2_chkdint.c
new file mode 100644
index 000000000..1de2c9140
--- /dev/null
+++ b/src/pcre2_chkdint.c
@@ -0,0 +1,79 @@
+/*************************************************
+*      Perl-Compatible Regular Expressions       *
+*************************************************/
+
+/* PCRE is a library of functions to support regular expressions whose syntax
+and semantics are as close as possible to those of the Perl 5 language.
+
+                     Written by Philip Hazel
+            Copyright (c) 2023 University of Cambridge
+
+-----------------------------------------------------------------------------
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright notice,
+      this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+
+    * Neither the name of the University of Cambridge nor the names of its
+      contributors may be used to endorse or promote products derived from
+      this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+-----------------------------------------------------------------------------
+*/
+
+/* This file contains functions to implement checked integer operation */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "pcre2_internal.h"
+
+/*************************************************
+*        Checked Integer Multiplication          *
+*************************************************/
+
+/*
+Arguments:
+  r         A pointer to PCRE2_SIZE to store the answer
+  a, b      Two positive integers
+
+Returns:    Bool indicating if the operation overflows
+
+It is modeled after C23's <stdckdint.h> interface
+The INT64_OR_DOUBLE type is a 64-bit integer type when available,
+otherwise double. */
+
+PCRE2_EXP_DEFN BOOL PCRE2_CALL_CONVENTION
+pcre2_ckd_smul(PCRE2_SIZE *r, int a, int b)
+{
+INT64_OR_DOUBLE m;
+
+#ifndef NDEBUG
+if (a < 0 || b < 0) abort();
+#endif
+
+m = (INT64_OR_DOUBLE)a * (INT64_OR_DOUBLE)b;
+if (m > (INT64_OR_DOUBLE)PCRE2_SIZE_MAX) return TRUE;
+
+*r = (PCRE2_SIZE)m;
+return FALSE;
+}
+
+/* End of pcre_chkdint.c */
diff --git a/src/pcre2_compile.c b/src/pcre2_compile.c
index edf7e82e6..b23369a79 100644
--- a/src/pcre2_compile.c
+++ b/src/pcre2_compile.c
@@ -7112,15 +7112,12 @@ for (;; pptr++)
 
         /* In the pre-compile phase, we don't actually do the replication. We
         just adjust the length as if we had. Do some paranoid checks for
-        potential integer overflow. The INT64_OR_DOUBLE type is a 64-bit
-        integer type when available, otherwise double. */
+        potential integer overflow. */
 
         if (lengthptr != NULL)
           {
-          PCRE2_SIZE delta = replicate*(1 + LINK_SIZE);
-          if ((INT64_OR_DOUBLE)replicate*
-                (INT64_OR_DOUBLE)(1 + LINK_SIZE) >
-                  (INT64_OR_DOUBLE)INT_MAX ||
+          PCRE2_SIZE delta;
+          if (pcre2_ckd_smul(&delta, replicate, 1 + LINK_SIZE) ||
               OFLOW_MAX - *lengthptr < delta)
             {
             *errorcodeptr = ERR20;
@@ -7282,15 +7279,12 @@ for (;; pptr++)
             {
             /* In the pre-compile phase, we don't actually do the replication.
             We just adjust the length as if we had. Do some paranoid checks for
-            potential integer overflow. The INT64_OR_DOUBLE type is a 64-bit
-            integer type when available, otherwise double. */
+            potential integer overflow. */
 
             if (lengthptr != NULL)
               {
-              PCRE2_SIZE delta = (repeat_min - 1)*length_prevgroup;
-              if ((INT64_OR_DOUBLE)(repeat_min - 1)*
-                    (INT64_OR_DOUBLE)length_prevgroup >
-                      (INT64_OR_DOUBLE)INT_MAX ||
+              PCRE2_SIZE delta;
+              if (pcre2_ckd_smul(&delta, repeat_min - 1, length_prevgroup) ||
                   OFLOW_MAX - *lengthptr < delta)
                 {
                 *errorcodeptr = ERR20;
@@ -7334,21 +7328,19 @@ for (;; pptr++)
           just adjust the length as if we had. For each repetition we must add
           1 to the length for BRAZERO and for all but the last repetition we
           must add 2 + 2*LINKSIZE to allow for the nesting that occurs. Do some
-          paranoid checks to avoid integer overflow. The INT64_OR_DOUBLE type
-          is a 64-bit integer type when available, otherwise double. */
+          paranoid checks to avoid integer overflow. */
 
           if (lengthptr != NULL && repeat_max > 0)
             {
-            PCRE2_SIZE delta = repeat_max*(length_prevgroup + 1 + 2 + 2*LINK_SIZE) -
-                        2 - 2*LINK_SIZE;   /* Last one doesn't nest */
-            if ((INT64_OR_DOUBLE)repeat_max *
-                  (INT64_OR_DOUBLE)(length_prevgroup + 1 + 2 + 2*LINK_SIZE)
-                    > (INT64_OR_DOUBLE)INT_MAX ||
+            PCRE2_SIZE delta;
+            if (pcre2_ckd_smul(&delta, repeat_max,
+                               length_prevgroup + 1 + 2 + 2*LINK_SIZE) ||
                 OFLOW_MAX - *lengthptr < delta)
               {
               *errorcodeptr = ERR20;
               return 0;
               }
+            delta -= (2 - 2*LINK_SIZE);   /* Last one doesn't nest */
             *lengthptr += delta;
             }
 
diff --git a/src/pcre2_internal.h b/src/pcre2_internal.h
index 92dd3138d..6469c6c71 100644
--- a/src/pcre2_internal.h
+++ b/src/pcre2_internal.h
@@ -156,8 +156,8 @@ pcre2_match() because of the way it backtracks. */
 #define PCRE2_SPTR CUSTOM_SUBJECT_PTR
 #endif
 
-/* When checking for integer overflow in pcre2_compile(), we need to handle
-large integers. If a 64-bit integer type is available, we can use that.
+/* When checking for integer overflow, we need to handle large integers.
+If a 64-bit integer type is available, we can use that.
 Otherwise we have to cast to double, which of course requires floating point
 arithmetic. Handle this by defining a macro for the appropriate type. */
 
@@ -2042,6 +2042,9 @@ extern void *       _pcre2_memmove(void *, const void *, size_t);
 #endif
 
 #endif  /* PCRE2_CODE_UNIT_WIDTH */
+
+extern BOOL         pcre2_ckd_smul(PCRE2_SIZE *, int, int);
+
 #endif  /* PCRE2_INTERNAL_H_IDEMPOTENT_GUARD */
 
 /* End of pcre2_internal.h */
diff --git a/src/pcre2test.c b/src/pcre2test.c
index 9c6a71f50..22d08fcd9 100644
--- a/src/pcre2test.c
+++ b/src/pcre2test.c
@@ -6836,7 +6836,7 @@ if (dbuffer != NULL)
 the number of code units that will be needed (though the buffer may have to be
 extended if replication is involved). */
 
-needlen = (size_t)((len+1) * code_unit_size);
+needlen = (len+1) * code_unit_size;
 if (dbuffer == NULL || needlen >= dbuffer_size)
   {
   while (needlen >= dbuffer_size)
@@ -6867,6 +6867,7 @@ while ((c = *p++) != 0)
 
   if (c == ']' && start_rep != NULL)
     {
+    PCRE2_SIZE d;
     long li;
     char *endptr;
 
@@ -6898,7 +6899,12 @@ while ((c = *p++) != 0)
       }
 
     replen = CAST8VAR(q) - start_rep;
-    needlen += replen * i;
+    if (pcre2_ckd_smul(&d, replen, i))
+      {
+      fprintf(outfile, "** Expanded content too large\n");
+      return PR_OK;
+      }
+    needlen += d;
 
     if (needlen >= dbuffer_size)
       {