diff --git a/src/devices/imagedev/cassette.cpp b/src/devices/imagedev/cassette.cpp
index adf59ca95eb..0a7671cffd5 100644
--- a/src/devices/imagedev/cassette.cpp
+++ b/src/devices/imagedev/cassette.cpp
@@ -265,26 +265,25 @@ image_init_result cassette_image_device::internal_load(bool is_create)
 {
 	casserr_t err;
 	int cassette_flags;
-	int is_writable;
+	bool is_writable;
 	device_image_interface *image = nullptr;
 	interface(image);
 
-	if (is_create || (length() == 0))
+	if (is_create)
 	{
-		/* creating an image */
+		// creating an image
 		err = cassette_create((void *)image, &image_ioprocs, &wavfile_format, m_create_opts, CASSETTE_FLAG_READWRITE|CASSETTE_FLAG_SAVEONEXIT, &m_cassette);
 		if (err)
 			goto error;
 	}
 	else
 	{
-		/* opening an image */
+		// opening an image
 		do
 		{
 			is_writable = !is_readonly();
 			cassette_flags = is_writable ? (CASSETTE_FLAG_READWRITE|CASSETTE_FLAG_SAVEONEXIT) : CASSETTE_FLAG_READONLY;
-			std::string fname;
-			err = cassette_open_choices((void *)image, &image_ioprocs, filetype().c_str(), m_formats, cassette_flags, &m_cassette);
+			err = cassette_open_choices((void *)image, &image_ioprocs, filetype(), m_formats, cassette_flags, &m_cassette);
 		}
 		while(err && is_writable);
 
diff --git a/src/lib/formats/cassimg.cpp b/src/lib/formats/cassimg.cpp
index 38403e598d2..cfa8e246a01 100644
--- a/src/lib/formats/cassimg.cpp
+++ b/src/lib/formats/cassimg.cpp
@@ -109,18 +109,18 @@ static void cassette_finishinit(casserr_t err, cassette_image *cassette, cassett
 
 
 
-static int good_format(const struct CassetteFormat *format, const char *extension, int flags)
+static bool good_format(const struct CassetteFormat *format, const std::string &extension, int flags)
 {
-	if (extension && !image_find_extension(format->extensions, extension))
-		return FALSE;
+	if (!extension.empty() && !image_find_extension(format->extensions, extension.c_str()))
+		return false;
 	if (((flags & CASSETTE_FLAG_READONLY) == 0) && !format->save)
-		return FALSE;
-	return TRUE;
+		return false;
+	return true;
 }
 
 
 
-casserr_t cassette_open_choices(void *file, const struct io_procs *procs, const char *extension,
+casserr_t cassette_open_choices(void *file, const struct io_procs *procs, const std::string &extension,
 	const struct CassetteFormat *const *formats, int flags, cassette_image **outcassette)
 {
 	casserr_t err;
diff --git a/src/lib/formats/cassimg.h b/src/lib/formats/cassimg.h
index 50542aacc73..5b585df5804 100644
--- a/src/lib/formats/cassimg.h
+++ b/src/lib/formats/cassimg.h
@@ -160,7 +160,7 @@ CASSETTE_FORMATLIST_EXTERN(cassette_default_formats);
 
 casserr_t cassette_open(void *file, const struct io_procs *procs,
 	const struct CassetteFormat *format, int flags, cassette_image **outcassette);
-casserr_t cassette_open_choices(void *file, const struct io_procs *procs, const char *extension,
+casserr_t cassette_open_choices(void *file, const struct io_procs *procs, const std::string &extension,
 	const struct CassetteFormat *const *formats, int flags, cassette_image **outcassette);
 casserr_t cassette_create(void *file, const struct io_procs *procs, const struct CassetteFormat *format,
 	const struct CassetteOptions *opts, int flags, cassette_image **outcassette);