diff --git a/src/pcre2_substitute.c b/src/pcre2_substitute.c
index 86c1d1e69..862ea9f73 100644
--- a/src/pcre2_substitute.c
+++ b/src/pcre2_substitute.c
@@ -134,7 +134,9 @@ for (; ptr < ptrend; ptr++)
     ptr -= 1;  /* Back to last code unit of escape */
     if (errorcode != 0)
       {
-      rc = errorcode;
+      /* errorcode from check_escape is positive, so must not be returned by
+      pcre2_substitute(). */
+      rc = PCRE2_ERROR_BADREPESCAPE;
       goto EXIT;
       }
 
diff --git a/testdata/testinput2 b/testdata/testinput2
index c2abdb890..8be78ff50 100644
--- a/testdata/testinput2
+++ b/testdata/testinput2
@@ -4201,6 +4201,12 @@
     123abc123\=substitute_overflow_length,replace=[1]x$1z
     123abc123\=substitute_overflow_length,replace=[0]x$1z
 
+/a(b)c/substitute_extended
+    ZabcZ\=replace=>${1:+ yes : no }
+    ZabcZ\=replace=>${1:+ \o{100} : \o{100} }
+    ZabcZ\=replace=>${1:+ \o{Z} : no }
+    ZabcZ\=replace=>${1:+ yes : \o{Z} }
+
 "((?=(?(?=(?(?=(?(?=()))))))))"
     a
 
diff --git a/testdata/testoutput2 b/testdata/testoutput2
index 7a582cd23..ccf209b5c 100644
--- a/testdata/testoutput2
+++ b/testdata/testoutput2
@@ -13818,6 +13818,16 @@ Failed: error -48: no more memory: 10 code units are needed
     123abc123\=substitute_overflow_length,replace=[0]x$1z
 Failed: error -48: no more memory: 10 code units are needed
 
+/a(b)c/substitute_extended
+    ZabcZ\=replace=>${1:+ yes : no }
+ 1: Z> yes Z
+    ZabcZ\=replace=>${1:+ \o{100} : \o{100} }
+ 1: Z> @ Z
+    ZabcZ\=replace=>${1:+ \o{Z} : no }
+Failed: error -57 at offset 9 in replacement: bad escape sequence in replacement string
+    ZabcZ\=replace=>${1:+ yes : \o{Z} }
+Failed: error -57 at offset 15 in replacement: bad escape sequence in replacement string
+
 "((?=(?(?=(?(?=(?(?=()))))))))"
     a
  0: