3 files changed, 11 insertions, 4 deletions
diff --git a/embed.fnc b/embed.fnc
index 1ba90415ff..4b04803a09 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -1885,7 +1885,7 @@ sR	|I32	|expect_number	|NN char **const pattern
 sn	|STRLEN	|sv_pos_u2b_forwards|NN const U8 *const start \
 		|NN const U8 *const send|STRLEN uoffset
 sn	|STRLEN	|sv_pos_u2b_midway|NN const U8 *const start \
-		|NN const U8 *send|const STRLEN uoffset|const STRLEN uend
+		|NN const U8 *send|STRLEN uoffset|const STRLEN uend
 s	|STRLEN	|sv_pos_u2b_cached|NN SV *const sv|NN MAGIC **const mgp \
 		|NN const U8 *const start|NN const U8 *const send \
 		|const STRLEN uoffset|STRLEN uoffset0|STRLEN boffset0
diff --git a/proto.h b/proto.h
index f25b40cf84..86658c17e1 100644
--- a/proto.h
+++ b/proto.h
@@ -5815,7 +5815,7 @@ STATIC STRLEN	S_sv_pos_u2b_forwards(const U8 *const start, const U8 *const send,
 #define PERL_ARGS_ASSERT_SV_POS_U2B_FORWARDS	\
 	assert(start); assert(send)
 
-STATIC STRLEN	S_sv_pos_u2b_midway(const U8 *const start, const U8 *send, const STRLEN uoffset, const STRLEN uend)
+STATIC STRLEN	S_sv_pos_u2b_midway(const U8 *const start, const U8 *send, STRLEN uoffset, const STRLEN uend)
 			__attribute__nonnull__(1)
 			__attribute__nonnull__(2);
 #define PERL_ARGS_ASSERT_SV_POS_U2B_MIDWAY	\
diff --git a/sv.c b/sv.c
index c38a318f74..45a98946ef 100644
--- a/sv.c
+++ b/sv.c
@@ -6110,7 +6110,7 @@ S_sv_pos_u2b_forwards(const U8 *const start, const U8 *const send,
    the passed in UTF-8 offset.  */
 static STRLEN
 S_sv_pos_u2b_midway(const U8 *const start, const U8 *send,
-		      const STRLEN uoffset, const STRLEN uend)
+		    STRLEN uoffset, const STRLEN uend)
 {
     STRLEN backw = uend - uoffset;
 
@@ -6120,7 +6120,14 @@ S_sv_pos_u2b_midway(const U8 *const start, const U8 *send,
 	/* The assumption is that going forwards is twice the speed of going
 	   forward (that's where the 2 * backw comes from).
 	   (The real figure of course depends on the UTF-8 data.)  */
-	return sv_pos_u2b_forwards(start, send, uoffset);
+	const U8 *s = start;
+
+	while (s < send && uoffset--)
+	    s += UTF8SKIP(s);
+	assert (s <= send);
+	if (s > send)
+	    s = send;
+	return s - start;
     }
 
     while (backw--) {