diff --git a/ChangeLog b/ChangeLog
index fe232d8..1a09dba 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -306,6 +306,9 @@ In addition, colour settings containing anything other than digits and
 semicolon are ignored, and the colour controls are no longer output for empty 
 strings.
 
+47. Detecting patterns that are too large inside the length-measuring loop
+saves processing ridiculously long patterns to their end.
+
 
 Version 10.22 29-July-2016
 --------------------------
diff --git a/src/pcre2_compile.c b/src/pcre2_compile.c
index de4a5b2..374fedf 100644
--- a/src/pcre2_compile.c
+++ b/src/pcre2_compile.c
@@ -4659,7 +4659,7 @@ for (;; pptr++)
 
   meta = META_CODE(*pptr);
   meta_arg = META_DATA(*pptr);
-
+  
   /* If we are in the pre-compile phase, accumulate the length used for the
   previous cycle of this loop, unless the next item is a quantifier. */
 
@@ -4693,6 +4693,11 @@ for (;; pptr++)
         return 0;
         }
       *lengthptr += (PCRE2_SIZE)(code - orig_code);
+      if (*lengthptr > MAX_PATTERN_SIZE)
+        {
+        *errorcodeptr = ERR20;   /* Pattern is too large */
+        return 0;
+        }
       code = orig_code;
       }
 
@@ -7334,7 +7339,6 @@ for (;;)
         }
       *lengthptr += length;
       }
-// if (lengthptr == NULL) fprintf(stderr, "~~group returns %d\n", okreturn);
     return okreturn;
     }
 
@@ -9075,6 +9079,8 @@ code = cworkspace;
 
 if (errorcode != 0) goto HAD_CB_ERROR;  /* Offset is in cb.erroroffset */
 
+/* This should be caught in compile_regex(), but just in case... */
+
 if (length > MAX_PATTERN_SIZE)
   {
   errorcode = ERR20;