https://github.com/PhilipHazel/pcre2/pull/22

--- a/src/pcre2_jit_compile.c
+++ b/src/pcre2_jit_compile.c
@@ -1251,10 +1251,13 @@ SLJIT_ASSERT(*cc == OP_ONCE || *cc == OP_BRA || *cc == OP_CBRA);
 SLJIT_ASSERT(*cc != OP_CBRA || common->optimized_cbracket[GET2(cc, 1 + LINK_SIZE)] != 0);
 SLJIT_ASSERT(start < EARLY_FAIL_ENHANCE_MAX);
 
+next_alt = cc + GET(cc, 1);
+if (*next_alt == OP_ALT)
+  fast_forward_allowed = FALSE;
+
 do
   {
   count = start;
-  next_alt = cc + GET(cc, 1);
   cc += 1 + LINK_SIZE + ((*cc == OP_CBRA) ? IMM2_SIZE : 0);
 
   while (TRUE)
@@ -1512,7 +1515,7 @@ do
         {
         count++;
 
-        if (fast_forward_allowed && *next_alt == OP_KET)
+        if (fast_forward_allowed)
           {
           common->fast_forward_bc_ptr = accelerated_start;
           common->private_data_ptrs[(accelerated_start + 1) - common->start] = ((*private_data_start) << 3) | type_skip;
@@ -1562,8 +1565,8 @@ do
   else if (result < count)
     result = count;
 
-  fast_forward_allowed = FALSE;
   cc = next_alt;
+  next_alt = cc + GET(cc, 1);
   }
 while (*cc == OP_ALT);
 
--- a/src/pcre2_jit_test.c
+++ b/src/pcre2_jit_test.c
@@ -352,6 +352,7 @@ static struct regression_test_case regression_test_cases[] = {
 	{ MU, A, 0, 0, ".[ab]?.", "xx" },
 	{ MU, A, 0, 0, "_[ab]+_*a", "_aa" },
 	{ MU, A, 0, 0, "#(A+)#\\d+", "#A#A#0" },
+	{ MU, A, 0, 0, "(?P<size>\\d+)m|M", "4M" },
 
 	/* Bracket repeats with limit. */
 	{ MU, A, 0, 0, "(?:(ab){2}){5}M", "abababababababababababM" },