diff --git a/numeric.c b/numeric.c
index fab4d66e39..c5ac72fef4 100644
--- a/numeric.c
+++ b/numeric.c
@@ -401,7 +401,7 @@ Perl_grok_bin_oct_hex(pTHX_ const char *start,
 
     const bool allow_underscores =
              cBOOL(input_flags & ( PERL_SCAN_ALLOW_UNDERSCORES
-                                  |PERL_SCAN_ALLOW_MEDIAL_UNDERSCORES));
+                                  |PERL_SCAN_ALLOW_MEDIAL_UNDERSCORES_ONLY));
     const char * s = start;
     const char * e = start + *len_p;
 
@@ -557,7 +557,7 @@ Perl_grok_bin_oct_hex(pTHX_ const char *start,
                  * set */
             && (   LIKELY(s > s0)
                 || UNLIKELY(! (  input_flags
-                               & PERL_SCAN_ALLOW_MEDIAL_UNDERSCORES))))
+                               & PERL_SCAN_ALLOW_MEDIAL_UNDERSCORES_ONLY))))
         {
             ++s;
 
diff --git a/perl.h b/perl.h
index c4c8577aed..8707b00ad2 100644
--- a/perl.h
+++ b/perl.h
@@ -8344,8 +8344,8 @@ EXTERN_C int flock(int fd, int op);
 /* Don't warn on overflow; output flag still set */
 #  define PERL_SCAN_SILENT_OVERFLOW                 0x80
 
-/* Forbid a leading underscore, which the other one doesn't */
-#  define PERL_SCAN_ALLOW_MEDIAL_UNDERSCORES        0x100
+/* grok_??? accept a stand-alone underscore between digits only in numbers */
+#  define PERL_SCAN_ALLOW_MEDIAL_UNDERSCORES_ONLY   0x100
 
 #endif
 
diff --git a/regcomp.c b/regcomp.c
index c6a2e6ee0e..56d3bb7986 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -5352,7 +5352,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
             I32 flags = PERL_SCAN_SILENT_OVERFLOW
                       | PERL_SCAN_SILENT_ILLDIGIT
                       | PERL_SCAN_NOTIFY_ILLDIGIT
-                      | PERL_SCAN_ALLOW_MEDIAL_UNDERSCORES
+                      | PERL_SCAN_ALLOW_MEDIAL_UNDERSCORES_ONLY
                       | PERL_SCAN_DISALLOW_PREFIX;
             STRLEN len = e - RExC_parse;
             NV overflow_value;