diff --git a/ChangeLog b/ChangeLog
index 107a6fe..0169af1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -14,10 +14,20 @@ hard-to-do issues such as #1887 in Bugzilla. The code is also cleaner because
 the old code had a number of fudges to try to reduce stack usage. It seems to 
 run no slower than the old code.
 
+A number of bugs in the refactored code were subsequently fixed during testing
+before release, but after the code was made available in the repository. Many
+of the bugs were discovered by fuzzing testing. These bugs were never in fully
+released code, but are noted here for the record.
+
+  (a) If a pattern had fewer capturing parentheses than the ovector supplied in 
+      the match data block, a memory error (detectable by ASAN) occurred after
+      a match, because the external block was being set from non-existent
+      internal ovector fields. Fixes oss-fuzz issue 781.
+
 2. Hardened pcre2test so as to reduce the number of bugs reported by fuzzers:
 
-   (a) Check for malloc failures when getting memory for the ovector (POSIX) or 
-       the match data block (non-POSIX). 
+  (a) Check for malloc failures when getting memory for the ovector (POSIX) or 
+      the match data block (non-POSIX). 
        
 3. In the 32-bit library in non-UTF mode, an attempt to find a Unicode property
 for a character with a code point greater than 0x10ffff (the Unicode maximum)
diff --git a/src/pcre2_match.c b/src/pcre2_match.c
index eec390a..734ee80 100644
--- a/src/pcre2_match.c
+++ b/src/pcre2_match.c
@@ -816,9 +816,11 @@ fprintf(stderr, "++ op=%d\n", *Fecode);
 
     ovector[0] = Fstart_match - mb->start_subject;
     ovector[1] = Feptr - mb->start_subject;
-    memcpy(ovector+2, Fovector, (oveccount - 1) * 2 * sizeof(PCRE2_SIZE));
-
+    
+    /* Set i to the smaller of the sizes of the external and frame ovectors. */
+    
     i = 2 * ((top_bracket + 1 > oveccount)? oveccount : top_bracket + 1);
+    memcpy(ovector + 2, Fovector, (i - 2) * sizeof(PCRE2_SIZE));
     while (--i >= Foffset_top + 2) ovector[i] = PCRE2_UNSET;
     return MATCH_MATCH;  /* Note: NOT RRETURN */