diff --git a/zconf.h b/zconf.h
index 7a9d8f21b54e6f405c15dea9c43fc56611fb0b28..9987a775530c0393e7c27b73b1e854b946d5ee47 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 10e445f216f20dba6dba085560888ca0e3768b6b..043019cda1db5ec2ca6a7c82acce4d559e9787d0 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 7a9d8f21b54e6f405c15dea9c43fc56611fb0b28..9987a775530c0393e7c27b73b1e854b946d5ee47 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