diff --git a/ChangeLog b/ChangeLog
index cf58f42..fb60852 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -73,6 +73,9 @@ or deserialization (the "load" or "save" commands).
 
 11. Fix memory leak in pcre2_serialize_decode() when the input is invalid.
 
+12. Fix potential NULL dereference in pcre2_callout_enumerate() if called with 
+a NULL pattern pointer when Unicode support is available.
+
 
 Version 10.23 14-February-2017
 ------------------------------
diff --git a/src/pcre2_pattern_info.c b/src/pcre2_pattern_info.c
index 0392a0b..5dd8ac5 100644
--- a/src/pcre2_pattern_info.c
+++ b/src/pcre2_pattern_info.c
@@ -261,11 +261,15 @@ pcre2_real_code *re = (pcre2_real_code *)code;
 pcre2_callout_enumerate_block cb;
 PCRE2_SPTR cc;
 #ifdef SUPPORT_UNICODE
-BOOL utf = (re->overall_options & PCRE2_UTF) != 0;
+BOOL utf;
 #endif
 
 if (re == NULL) return PCRE2_ERROR_NULL;
 
+#ifdef SUPPORT_UNICODE
+utf = (re->overall_options & PCRE2_UTF) != 0;
+#endif
+
 /* Check that the first field in the block is the magic number. If it is not,
 return with PCRE2_ERROR_BADMAGIC. */