diff --git a/ChangeLog b/ChangeLog
index 151141f..0869658 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -41,6 +41,9 @@ some minor bugs and Perl incompatibilities were fixed, including:
   (g) A hyphen appearing immediately after a POSIX character class (for example 
       /[[:ascii:]-z]/) now generates an error. Perl does accept this as a 
       literal, but gives a warning, so it seems best to fail it in PCRE. 
+      
+  (h) An empty \Q\E sequence may appear after a callout that precedes an 
+      assertion condition (it is, of course, ignored).
 
 One effect of the refactoring is that some error numbers and messages have
 changed, and the pattern offset given for compiling errors is not always the
diff --git a/src/pcre2_compile.c b/src/pcre2_compile.c
index 046faff..de4a5b2 100644
--- a/src/pcre2_compile.c
+++ b/src/pcre2_compile.c
@@ -2321,6 +2321,12 @@ while (ptr < ptrend)
       }
     else
       {
+      if (expect_cond_assert > 0)   /* A literal is not allowed if we are */
+        {                           /* expecting a conditional assertion, */
+        ptr--;                      /* but an empty \Q\E sequence is OK.  */
+        errorcode = ERR28;
+        goto FAILED;
+        }
       if (!inverbname && after_manual_callout-- <= 0)
         parsed_pattern = manage_callouts(thisptr, &previous_callout, options,
           parsed_pattern, cb);
@@ -2992,17 +2998,17 @@ while (ptr < ptrend)
           goto FAILED;
           }
         ptr = tempptr + 2;
-        
+
         /* Perl treats a hyphen after a POSIX class as a literal, not the
         start of a range. However, it gives a warning in its warning mode. PCRE
         does not have a warning mode, so we give an error, because this is
         likely an error on the user's part. */
-        
+
         if (ptr < ptrend && *ptr == CHAR_MINUS)
           {
           errorcode = ERR50;
           goto FAILED;
-          }     
+          }
 
         /* When PCRE2_UCP is set, some of the POSIX classes are converted to
         use Unicode properties \p or \P or, in one case, \h or \H. The
@@ -4938,13 +4944,13 @@ for (;; pptr++)
           automatically handled by the use of OP_CLASS or OP_NCLASS, but an
           explicit range is needed for OP_XCLASS. Setting a flag here
           causes the range to be generated later when it is known that
-          OP_XCLASS is required. In the 8-bit library this is relevant only in 
+          OP_XCLASS is required. In the 8-bit library this is relevant only in
           utf mode, since no wide characters can exist otherwise. */
 
           default:
 #if PCRE2_CODE_UNIT_WIDTH == 8
           if (utf)
-#endif 
+#endif
           match_all_or_no_wide_chars |= local_negate;
           break;
           }
@@ -7941,7 +7947,7 @@ Arguments:
 
 Returns:     new value of pptr
              NULL if META_END is reached - should never occur
-               or for an unknown meta value - likewise 
+               or for an unknown meta value - likewise
 */
 
 static uint32_t *
@@ -7952,7 +7958,7 @@ uint32_t nestlevel = 0;
 for (pptr += 1;; pptr++)
   {
   uint32_t meta = META_CODE(*pptr);
-  
+
   switch(meta)
     {
     default:  /* Just skip over most items */
@@ -8517,7 +8523,7 @@ cb->erroroffset = PCRE2_UNSET;
 for (pptr = cb->parsed_pattern; *pptr != META_END; pptr++)
   {
   if (*pptr < META_END) continue;  /* Literal */
-  
+
   switch (META_CODE(*pptr))
     {
     default:
diff --git a/testdata/testinput2 b/testdata/testinput2
index f8a0545..bd13a85 100644
--- a/testdata/testinput2
+++ b/testdata/testinput2
@@ -4952,4 +4952,8 @@ a)"xI
 
 /[:[:alnum:]-[[a:lnum:]+/
 
+/((?(?C'')\QX\E(?!((?(?C'')(?!X=X));=)r*X=X));=)/
+
+/((?(?C'')\Q\E(?!((?(?C'')(?!X=X));=)r*X=X));=)/
+
 # End of testinput2 
diff --git a/testdata/testoutput2 b/testdata/testoutput2
index 9f8ccb0..57bf862 100644
--- a/testdata/testoutput2
+++ b/testdata/testoutput2
@@ -15434,6 +15434,11 @@ Failed: error 128 at offset 63: assertion expected after (?( or (?(?C)
 /[:[:alnum:]-[[a:lnum:]+/
 Failed: error 150 at offset 11: invalid range in character class
 
+/((?(?C'')\QX\E(?!((?(?C'')(?!X=X));=)r*X=X));=)/
+Failed: error 128 at offset 11: assertion expected after (?( or (?(?C)
+
+/((?(?C'')\Q\E(?!((?(?C'')(?!X=X));=)r*X=X));=)/
+
 # End of testinput2 
 Error -63: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data