diff --git a/zconf.h b/zconf.h
index 7a9d8f2..9987a77 100644
--- a/zconf.h
+++ b/zconf.h
@@ -218,7 +218,7 @@
 #  endif
 #endif
 
-#if ( defined(ZLIB_CONST) || defined(__cplusplus) ) && !defined(z_const)
+#if defined(ZLIB_CONST) && !defined(z_const)
 #  define z_const const
 #else
 #  define z_const
diff --git a/zconf.h.cmakein b/zconf.h.cmakein
index 10e445f..043019c 100644
--- a/zconf.h.cmakein
+++ b/zconf.h.cmakein
@@ -220,7 +220,7 @@
 #  endif
 #endif
 
-#if ( defined(ZLIB_CONST) || defined(__cplusplus) ) && !defined(z_const)
+#if defined(ZLIB_CONST) && !defined(z_const)
 #  define z_const const
 #else
 #  define z_const
diff --git a/zconf.h.in b/zconf.h.in
index 7a9d8f2..9987a77 100644
--- a/zconf.h.in
+++ b/zconf.h.in
@@ -218,7 +218,7 @@
 #  endif
 #endif
 
-#if ( defined(ZLIB_CONST) || defined(__cplusplus) ) && !defined(z_const)
+#if defined(ZLIB_CONST) && !defined(z_const)
 #  define z_const const
 #else
 #  define z_const