diff --git a/binding-mri/font-binding.cpp b/binding-mri/font-binding.cpp
index b270170..66b6339 100644
--- a/binding-mri/font-binding.cpp
+++ b/binding-mri/font-binding.cpp
@@ -33,8 +33,13 @@ RB_METHOD(fontDoesExist)
 {
 	RB_UNUSED_PARAM;
 
-	const char *name;
-	rb_get_args(argc, argv, "z", &name RB_ARG_END);
+	const char *name = 0;
+	VALUE nameObj;
+
+	rb_get_args(argc, argv, "o", &nameObj RB_ARG_END);
+
+	if (rb_type(nameObj) == RUBY_T_STRING)
+		name = rb_string_value_cstr(&nameObj);
 
 	return rb_bool_new(Font::doesExist(name));
 }
diff --git a/binding-mruby/font-binding.cpp b/binding-mruby/font-binding.cpp
index 7ffad01..c5b82d7 100644
--- a/binding-mruby/font-binding.cpp
+++ b/binding-mruby/font-binding.cpp
@@ -30,8 +30,13 @@ DEF_TYPE(Font);
 
 MRB_FUNCTION(fontDoesExist)
 {
-	const char *name;
-	mrb_get_args(mrb, "z", &name);
+	const char *name = 0;
+	mrb_value nameObj;
+
+	mrb_get_args(mrb, "o", &nameObj);
+
+	if (mrb_string_p(nameObj))
+		name = mrb_string_value_cstr(mrb, &nameObj);
 
 	return mrb_bool_value(Font::doesExist(name));
 }
diff --git a/src/font.cpp b/src/font.cpp
index a5dbed5..1d0d74e 100644
--- a/src/font.cpp
+++ b/src/font.cpp
@@ -247,6 +247,9 @@ Color FontPrivate::defaultColorTmp(255, 255, 255, 255);
 
 bool Font::doesExist(const char *name)
 {
+	if (!name)
+		return false;
+
 	return shState->fontState().fontPresent(name);
 }