diff --git a/zconf.h b/zconf.h
index 8a46a58..c71cade 100644
--- a/zconf.h
+++ b/zconf.h
@@ -426,7 +426,9 @@ typedef uLong FAR uLongf;
 #endif
 
 #ifdef _WIN32
-#  include <stddef.h>           /* for wchar_t */
+#  ifndef Z_SOLO
+#    include <stddef.h>         /* for wchar_t */
+#  endif
 #endif
 
 /* a little trick to accommodate both "#define _LARGEFILE64_SOURCE" and
diff --git a/zconf.h.cmakein b/zconf.h.cmakein
index b6ca59a..1d31b67 100644
--- a/zconf.h.cmakein
+++ b/zconf.h.cmakein
@@ -428,7 +428,9 @@ typedef uLong FAR uLongf;
 #endif
 
 #ifdef _WIN32
-#  include <stddef.h>           /* for wchar_t */
+#  ifndef Z_SOLO
+#    include <stddef.h>         /* for wchar_t */
+#  endif
 #endif
 
 /* a little trick to accommodate both "#define _LARGEFILE64_SOURCE" and
diff --git a/zconf.h.in b/zconf.h.in
index 8a46a58..c71cade 100644
--- a/zconf.h.in
+++ b/zconf.h.in
@@ -426,7 +426,9 @@ typedef uLong FAR uLongf;
 #endif
 
 #ifdef _WIN32
-#  include <stddef.h>           /* for wchar_t */
+#  ifndef Z_SOLO
+#    include <stddef.h>         /* for wchar_t */
+#  endif
 #endif
 
 /* a little trick to accommodate both "#define _LARGEFILE64_SOURCE" and