diff --git a/binding-mri/binding-mri.cpp b/binding-mri/binding-mri.cpp
index 1cffac1..130c763 100644
--- a/binding-mri/binding-mri.cpp
+++ b/binding-mri/binding-mri.cpp
@@ -226,7 +226,7 @@ static void runRMXPScripts()
 		VALUE scriptString = rb_ary_entry(script, 2);
 
 		int result = Z_OK;
-		ulong bufferLen;
+		unsigned long bufferLen;
 
 		while (true)
 		{
diff --git a/binding-mruby/binding-mruby.cpp b/binding-mruby/binding-mruby.cpp
index cac342a..e93e752 100644
--- a/binding-mruby/binding-mruby.cpp
+++ b/binding-mruby/binding-mruby.cpp
@@ -303,7 +303,7 @@ runRMXPScripts(mrb_state *mrb, mrbc_context *ctx)
 		(void) scriptChksum;
 
 		int result = Z_OK;
-		ulong bufferLen;
+		unsigned long bufferLen;
 
 		while (true)
 		{