diff --git a/src/devices/disk/mo.c b/src/devices/disk/mo.c
index 9119d12..4d41690 100644
--- a/src/devices/disk/mo.c
+++ b/src/devices/disk/mo.c
@@ -2575,7 +2575,7 @@ mo_format(mo_t *dev)
 
 	ret = (int)SetEndOfFile(fh);
 
-	if(ret)
+	if(!ret)
 	{
 		DEBUG("MO %i: Failed to truncate image file to 0\n", dev->id);
 		return;
@@ -2592,7 +2592,7 @@ mo_format(mo_t *dev)
 
 	ret = (int)SetEndOfFile(fh);
 
-	if(ret)
+	if(!ret)
 	{
 		DEBUG("MO %i: Failed to truncate image file to %llu\n", dev->id, size);
 		return;
@@ -2655,3 +2655,4 @@ mo_erase(mo_t *dev)
 
 	return 1;
 }
+