diff --git a/Zend/zend_strtod_int.h b/Zend/zend_strtod_int.h
index 79b993f7dbd9f..06a02618e9e6a 100644
--- a/Zend/zend_strtod_int.h
+++ b/Zend/zend_strtod_int.h
@@ -16,6 +16,8 @@
    +----------------------------------------------------------------------+
 */
 
+/* internal header; not supposed to be installed; FIXME but unfortunately is */
+
 #ifndef ZEND_STRTOD_INT_H
 #define ZEND_STRTOD_INT_H
 
diff --git a/ext/gmp/php_gmp_int.h b/ext/gmp/php_gmp_int.h
index d67fdd5c62236..32f1d32f592ab 100644
--- a/ext/gmp/php_gmp_int.h
+++ b/ext/gmp/php_gmp_int.h
@@ -1,3 +1,5 @@
+/* interface header; needs to be installed; FIXME rename? */
+
 #ifndef incl_PHP_GMP_INT_H
 #define incl_PHP_GMP_INT_H
 
diff --git a/ext/pdo_dblib/php_pdo_dblib_int.h b/ext/pdo_dblib/php_pdo_dblib_int.h
index 8f8d0e3c827eb..2067d944c7182 100644
--- a/ext/pdo_dblib/php_pdo_dblib_int.h
+++ b/ext/pdo_dblib/php_pdo_dblib_int.h
@@ -15,6 +15,8 @@
   +----------------------------------------------------------------------+
 */
 
+/* internal header; not supposed to be installed */
+
 #ifndef PHP_PDO_DBLIB_INT_H
 #define PHP_PDO_DBLIB_INT_H
 
diff --git a/ext/pdo_firebird/php_pdo_firebird_int.h b/ext/pdo_firebird/php_pdo_firebird_int.h
index dc1e4bb7f4086..2b8d00a4e37e6 100644
--- a/ext/pdo_firebird/php_pdo_firebird_int.h
+++ b/ext/pdo_firebird/php_pdo_firebird_int.h
@@ -14,6 +14,8 @@
   +----------------------------------------------------------------------+
 */
 
+/* internal header; not supposed to be installed */
+
 #ifndef PHP_PDO_FIREBIRD_INT_H
 #define PHP_PDO_FIREBIRD_INT_H
 
diff --git a/ext/pdo_mysql/php_pdo_mysql_int.h b/ext/pdo_mysql/php_pdo_mysql_int.h
index b2e15e3080d5a..9c78813d5f249 100644
--- a/ext/pdo_mysql/php_pdo_mysql_int.h
+++ b/ext/pdo_mysql/php_pdo_mysql_int.h
@@ -16,6 +16,8 @@
   +----------------------------------------------------------------------+
 */
 
+/* internal header; not supposed to be installed */
+
 #ifndef PHP_PDO_MYSQL_INT_H
 #define PHP_PDO_MYSQL_INT_H
 
diff --git a/ext/pdo_odbc/php_pdo_odbc_int.h b/ext/pdo_odbc/php_pdo_odbc_int.h
index e082ae7512355..473d70ff70763 100644
--- a/ext/pdo_odbc/php_pdo_odbc_int.h
+++ b/ext/pdo_odbc/php_pdo_odbc_int.h
@@ -14,6 +14,8 @@
   +----------------------------------------------------------------------+
 */
 
+/* internal header; not supposed to be installed */
+
 #ifdef PHP_WIN32
 # define PDO_ODBC_TYPE	"Win32"
 #endif
diff --git a/ext/pdo_pgsql/php_pdo_pgsql_int.h b/ext/pdo_pgsql/php_pdo_pgsql_int.h
index 3cd0b005fcc55..fc9f1664cc3d4 100644
--- a/ext/pdo_pgsql/php_pdo_pgsql_int.h
+++ b/ext/pdo_pgsql/php_pdo_pgsql_int.h
@@ -16,6 +16,8 @@
   +----------------------------------------------------------------------+
 */
 
+/* internal header; not supposed to be installed */
+
 #ifndef PHP_PDO_PGSQL_INT_H
 #define PHP_PDO_PGSQL_INT_H
 
diff --git a/ext/standard/php_dir_int.h b/ext/standard/php_dir_int.h
index a359cb725d085..f9d63e78661a1 100644
--- a/ext/standard/php_dir_int.h
+++ b/ext/standard/php_dir_int.h
@@ -12,6 +12,8 @@
    +----------------------------------------------------------------------+
  */
 
+/* internal header; not supposed to be installed; FIXME but unfortunately is */
+
 #ifndef PHP_DIR_INT_H
 #define PHP_DIR_INT_H
 
diff --git a/main/streams/php_streams_int.h b/main/streams/php_streams_int.h
index a3c55bdd4f066..7580088fba316 100644
--- a/main/streams/php_streams_int.h
+++ b/main/streams/php_streams_int.h
@@ -14,6 +14,8 @@
   +----------------------------------------------------------------------+
 */
 
+/* internal header; not supposed to be installed; FIXME but unfortunately is */
+
 #if ZEND_DEBUG
 
 #define emalloc_rel_orig(size)	\