diff --git a/tests/image-fuzzer/qcow2/fuzz.py b/tests/image-fuzzer/qcow2/fuzz.py
index 154dc06cc096..c58bf110054c 100644
--- a/tests/image-fuzzer/qcow2/fuzz.py
+++ b/tests/image-fuzzer/qcow2/fuzz.py
@@ -36,11 +36,11 @@
 UINT64_V = UINT32_V + [0x1000000, 0x10000000, 0x100000000, UINT64//4,
                        UINT64//2 - 1, UINT64//2, UINT64//2 + 1, UINT64 - 1,
                        UINT64]
-STRING_V = ['%s%p%x%d', '.1024d', '%.2049d', '%p%p%p%p', '%x%x%x%x',
-            '%d%d%d%d', '%s%s%s%s', '%99999999999s', '%08x', '%%20d', '%%20n',
-            '%%20x', '%%20s', '%s%s%s%s%s%s%s%s%s%s', '%p%p%p%p%p%p%p%p%p%p',
-            '%#0123456x%08x%x%s%p%d%n%o%u%c%h%l%q%j%z%Z%t%i%e%g%f%a%C%S%08x%%',
-            '%s x 129', '%x x 257']
+BYTES_V = [b'%s%p%x%d', b'.1024d', b'%.2049d', b'%p%p%p%p', b'%x%x%x%x',
+           b'%d%d%d%d', b'%s%s%s%s', b'%99999999999s', b'%08x', b'%%20d', b'%%20n',
+           b'%%20x', b'%%20s', b'%s%s%s%s%s%s%s%s%s%s', b'%p%p%p%p%p%p%p%p%p%p',
+           b'%#0123456x%08x%x%s%p%d%n%o%u%c%h%l%q%j%z%Z%t%i%e%g%f%a%C%S%08x%%',
+           b'%s x 129', b'%x x 257']
 
 
 def random_from_intervals(intervals):
@@ -76,12 +76,12 @@ def random_bits(bit_ranges):
     return val
 
 
-def truncate_string(strings, length):
-    """Return strings truncated to specified length."""
-    if type(strings) == list:
-        return [s[:length] for s in strings]
+def truncate_bytes(sequences, length):
+    """Return sequences truncated to specified length."""
+    if type(sequences) == list:
+        return [s[:length] for s in sequences]
     else:
-        return strings[:length]
+        return sequences[:length]
 
 
 def validator(current, pick, choices):
@@ -110,12 +110,12 @@ def bit_validator(current, bit_ranges):
     return validator(current, random_bits, bit_ranges)
 
 
-def string_validator(current, strings):
-    """Return a random string value from the list not equal to the current.
+def bytes_validator(current, sequences):
+    """Return a random bytes value from the list not equal to the current.
 
     This function is useful for selection from valid values except current one.
     """
-    return validator(current, random.choice, strings)
+    return validator(current, random.choice, sequences)
 
 
 def selector(current, constraints, validate=int_validator):
@@ -283,9 +283,9 @@ def header_length(current):
 def bf_name(current):
     """Fuzz the backing file name."""
     constraints = [
-        truncate_string(STRING_V, len(current))
+        truncate_bytes(BYTES_V, len(current))
     ]
-    return selector(current, constraints, string_validator)
+    return selector(current, constraints, bytes_validator)
 
 
 def ext_magic(current):
@@ -303,10 +303,10 @@ def ext_length(current):
 def bf_format(current):
     """Fuzz backing file format in the corresponding header extension."""
     constraints = [
-        truncate_string(STRING_V, len(current)),
-        truncate_string(STRING_V, (len(current) + 7) & ~7)  # Fuzz padding
+        truncate_bytes(BYTES_V, len(current)),
+        truncate_bytes(BYTES_V, (len(current) + 7) & ~7)  # Fuzz padding
     ]
-    return selector(current, constraints, string_validator)
+    return selector(current, constraints, bytes_validator)
 
 
 def feature_type(current):
@@ -324,10 +324,10 @@ def feature_bit_number(current):
 def feature_name(current):
     """Fuzz feature name field of a feature name table header extension."""
     constraints = [
-        truncate_string(STRING_V, len(current)),
-        truncate_string(STRING_V, 46)  # Fuzz padding (field length = 46)
+        truncate_bytes(BYTES_V, len(current)),
+        truncate_bytes(BYTES_V, 46)  # Fuzz padding (field length = 46)
     ]
-    return selector(current, constraints, string_validator)
+    return selector(current, constraints, bytes_validator)
 
 
 def l1_entry(current):