diff --git a/include/maxscale/pcre2.h b/include/maxscale/pcre2.h
index 77d7d6976..de28c74aa 100644
--- a/include/maxscale/pcre2.h
+++ b/include/maxscale/pcre2.h
@@ -27,14 +27,16 @@
 
 #include <maxscale/cdefs.h>
 
-#ifndef PCRE2_CODE_UNIT_WIDTH
+MXS_BEGIN_DECLS
+
+#if defined(PCRE2_CODE_UNIT_WIDTH)
+#error PCRE2_CODE_UNIT_WIDTH already defined. Do not define, and include <maxscale/pcre2.h>.
+#else
 #define PCRE2_CODE_UNIT_WIDTH 8
 #endif
 
 #include <pcre2.h>
 
-MXS_BEGIN_DECLS
-
 typedef enum
 {
     MXS_PCRE2_MATCH,
diff --git a/server/modules/filter/regexfilter/regexfilter.c b/server/modules/filter/regexfilter/regexfilter.c
index 21fe8e433..918cc95f0 100644
--- a/server/modules/filter/regexfilter/regexfilter.c
+++ b/server/modules/filter/regexfilter/regexfilter.c
@@ -11,17 +11,17 @@
  * Public License.
  */
 
-#define PCRE2_CODE_UNIT_WIDTH 8
+#include <maxscale/cdefs.h>
+#include <string.h>
 #include <stdio.h>
+#include <maxscale/alloc.h>
+#include <maxscale/atomic.h>
+#include <maxscale/config.h>
 #include <maxscale/filter.h>
+#include <maxscale/log_manager.h>
 #include <maxscale/modinfo.h>
 #include <maxscale/modutil.h>
-#include <maxscale/log_manager.h>
-#include <string.h>
-#include <pcre2.h>
-#include <maxscale/atomic.h>
-#include <maxscale/alloc.h>
-#include <maxscale/config.h>
+#include <maxscale/pcre2.h>
 
 /**
  * @file regexfilter.c - a very simple regular expression rewrite filter.