diff --git a/ext/iconv/config.m4 b/ext/iconv/config.m4
index 4d0dc36489833..efe79be140242 100644
--- a/ext/iconv/config.m4
+++ b/ext/iconv/config.m4
@@ -83,6 +83,17 @@ int main(void) {
   AS_VAR_IF([php_cv_iconv_errno], [yes],,
     [AC_MSG_FAILURE([The iconv check failed, 'errno' is missing.])])
 
+  dnl iconv on some platforms (NetBSD pre-10, Solaris) may have a non-standard
+  dnl const input parameter; libiconv may imitate this on those platforms.
+  AC_CACHE_CHECK([if iconv input parameter is const (non-standard)], [php_cv_iconv_const],
+    [AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+#include <iconv.h>
+
+size_t iconv(iconv_t cd, const char **src, size_t *srcleft, char **dst, size_t *dstleft);
+    ])],
+    [php_cv_iconv_const=const],
+    [php_cv_iconv_const=])])
+
   AC_CACHE_CHECK([if iconv supports //IGNORE], [php_cv_iconv_ignore],
     [AC_RUN_IFELSE([AC_LANG_SOURCE([
 #include <iconv.h>
@@ -120,7 +131,7 @@ int main(void) {
   PHP_NEW_EXTENSION([iconv],
     [iconv.c],
     [$ext_shared],,
-    [-DZEND_ENABLE_STATIC_TSRMLS_CACHE=1])
+    [-DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -DICONV_CONST=$php_cv_iconv_const])
   PHP_SUBST([ICONV_SHARED_LIBADD])
   PHP_INSTALL_HEADERS([ext/iconv], [php_iconv.h])
 fi
diff --git a/ext/iconv/config.w32 b/ext/iconv/config.w32
index d99c53fb93634..523adccb68295 100644
--- a/ext/iconv/config.w32
+++ b/ext/iconv/config.w32
@@ -13,7 +13,7 @@ if (PHP_ICONV != "no") {
 		AC_DEFINE("HAVE_LIBICONV", 1, "Define to 1 if you have the 'libiconv' function.");
 		AC_DEFINE("ICONV_ALIASED_LIBICONV", 1, "Define to 1 if 'iconv()' is aliased to 'libiconv()'.");
 		AC_DEFINE("PHP_ICONV_IMPL", "\"libiconv\"", "The iconv implementation.");
-		ADD_FLAG("CFLAGS_ICONV", "/D PHP_ICONV_EXPORTS ");
+		ADD_FLAG("CFLAGS_ICONV", "/D PHP_ICONV_EXPORTS /D ICONV_CONST ");
 		if (!PHP_ICONV_SHARED) {
 			ADD_DEF_FILE("ext\\iconv\\php_iconv.def");
 		}
diff --git a/ext/iconv/iconv.c b/ext/iconv/iconv.c
index 4241b7c2887fb..85eae71d74a69 100644
--- a/ext/iconv/iconv.c
+++ b/ext/iconv/iconv.c
@@ -43,14 +43,6 @@
 #undef iconv
 #endif
 
-#if defined(__NetBSD__)
-// unfortunately, netbsd has still the old non posix conformant signature
-// libiconv tends to match the eventual system's iconv too.
-#define ICONV_CONST const
-#else
-#define ICONV_CONST
-#endif
-
 #include "zend_smart_str.h"
 #include "ext/standard/base64.h"
 #include "ext/standard/quot_print.h"