diff --git a/Zend/zend_smart_str.c b/Zend/zend_smart_str.c
index 5132043c60e..689989059c2 100644
--- a/Zend/zend_smart_str.c
+++ b/Zend/zend_smart_str.c
@@ -14,9 +14,11 @@
    +----------------------------------------------------------------------+
  */
 
-#include <zend.h>
 #include "zend_smart_str.h"
 #include "zend_smart_string.h"
+#include "zend_globals_macros.h" // for EG()
+#include "zend_globals.h" // struct _zend_executor_globals
+#include "zend_strtod.h" // for zend_gcvt()
 
 #define SMART_STR_OVERHEAD   (ZEND_MM_OVERHEAD + _ZSTR_HEADER_SIZE + 1)
 #define SMART_STR_START_SIZE 256
diff --git a/Zend/zend_smart_str.h b/Zend/zend_smart_str.h
index e271835e41d..ac5b18db97e 100644
--- a/Zend/zend_smart_str.h
+++ b/Zend/zend_smart_str.h
@@ -17,10 +17,15 @@
 #ifndef ZEND_SMART_STR_H
 #define ZEND_SMART_STR_H
 
-#include <zend.h>
-#include "zend_globals.h"
 #include "zend_smart_str_public.h"
 
+#include "zend_operators.h" // for zend_print_long_to_buf()
+#include "zend_portability.h" // for BEGIN_EXTERN_C
+#include "zend_string.h"
+
+// forward declarations
+typedef struct _zval_struct zval;
+
 BEGIN_EXTERN_C()
 
 ZEND_API void ZEND_FASTCALL smart_str_erealloc(smart_str *str, size_t len);
diff --git a/Zend/zend_smart_str_public.h b/Zend/zend_smart_str_public.h
index e81a6839b3b..84fc3758ae7 100644
--- a/Zend/zend_smart_str_public.h
+++ b/Zend/zend_smart_str_public.h
@@ -17,6 +17,11 @@
 #ifndef ZEND_SMART_STR_PUBLIC_H
 #define ZEND_SMART_STR_PUBLIC_H
 
+#include <stddef.h> // for size_t
+
+// forward declarations
+typedef struct _zend_string zend_string;
+
 typedef struct {
 	/** See smart_str_extract() */
 	zend_string *s;
diff --git a/Zend/zend_smart_string.h b/Zend/zend_smart_string.h
index 8149b29fb33..08eb6a8eced 100644
--- a/Zend/zend_smart_string.h
+++ b/Zend/zend_smart_string.h
@@ -20,8 +20,9 @@
 
 #include "zend_smart_string_public.h"
 
-#include <stdlib.h>
-#include <zend.h>
+#include "zend_alloc.h" // for pefree()
+#include "zend_operators.h" // for zend_print_long_to_buf()
+#include "zend_portability.h" // for ZEND_FASTCALL
 
 /* wrapper */
 
diff --git a/Zend/zend_smart_string_public.h b/Zend/zend_smart_string_public.h
index 543e1d37a4e..e61bdd2d36f 100644
--- a/Zend/zend_smart_string_public.h
+++ b/Zend/zend_smart_string_public.h
@@ -18,7 +18,7 @@
 #ifndef PHP_SMART_STRING_PUBLIC_H
 #define PHP_SMART_STRING_PUBLIC_H
 
-#include <sys/types.h>
+#include <stddef.h> // for size_t
 
 typedef struct {
 	char *c;