diff --git a/reimplement/set.py b/reimplement/set.py
index 5ac4c5f..befc3ed 100644
--- a/reimplement/set.py
+++ b/reimplement/set.py
@@ -260,10 +260,10 @@ def decode_set(encoded_str: str, Mshift: int) -> List[int]:
 
 
 def rpmsetcmp(str1: str, str2: str) -> int:
-    if str1[:3] == "set:":
-        str1 = str1[3:]
-    if str2[:3] == "set:":
-        str2 = str2[3:]
+    if str1.startswith("set:"):
+        str1 = str1[4:]
+    if str2.startswith("set:"):
+        str2 = str2[4:]
 
     bpp1, Mshift1 = decode_set_init(str1)
     bpp2, Mshift2 = decode_set_init(str2)
@@ -288,21 +288,28 @@ def rpmsetcmp(str1: str, str2: str) -> int:
 
     while i < len(hash_values1) and j < len(hash_values2):
         if hash_values1[i] < hash_values2[j]:
-            ge = False
+            le = False
             i += 1
         elif hash_values1[i] > hash_values2[j]:
-            le = False
+            ge = False
             j += 1
         else:
             i += 1
             j += 1
 
+    if i < len(hash_values1):
+        le = False
+    if j < len(hash_values2):
+        ge = False
+
     if ge and le:
         return 0
     elif ge:
         return 1
-    else:
+    elif le:
         return -1
+    else:
+        return -2
 
 
 def set_new() -> Set:
diff --git a/tests/test_reimplement_set.py b/tests/test_reimplement_set.py
index 917a241..5f60867 100644
--- a/tests/test_reimplement_set.py
+++ b/tests/test_reimplement_set.py
@@ -81,6 +81,36 @@ class DownsampleSetTest(unittest.TestCase):
         self.assertEqual(rpmset.downsample_set([8, 10, 14], 3), [0, 2, 6])
 
 
+class RpmSetCmpTest(unittest.TestCase):
+    def encode_values(self, values, bpp=8):
+        return rpmset.encode_set(values, bpp)
+
+    def test_returns_zero_for_equal_sets(self):
+        set1 = self.encode_values([1, 3, 5])
+        set2 = self.encode_values([1, 3, 5])
+        self.assertEqual(rpmset.rpmsetcmp(set1, set2), 0)
+
+    def test_accepts_set_prefix(self):
+        set1 = "set:" + self.encode_values([1, 3, 5])
+        set2 = self.encode_values([1, 3, 5])
+        self.assertEqual(rpmset.rpmsetcmp(set1, set2), 0)
+
+    def test_returns_one_when_first_set_is_superset(self):
+        set1 = self.encode_values([1, 3, 5])
+        set2 = self.encode_values([1, 3])
+        self.assertEqual(rpmset.rpmsetcmp(set1, set2), 1)
+
+    def test_returns_minus_one_when_first_set_is_subset(self):
+        set1 = self.encode_values([1, 3])
+        set2 = self.encode_values([1, 3, 5])
+        self.assertEqual(rpmset.rpmsetcmp(set1, set2), -1)
+
+    def test_returns_minus_two_for_incomparable_sets(self):
+        set1 = self.encode_values([1, 3, 7])
+        set2 = self.encode_values([1, 3, 5])
+        self.assertEqual(rpmset.rpmsetcmp(set1, set2), -2)
+
+
 class ModuleEntrypointTest(unittest.TestCase):
     def test_module_has_no_main_side_effects(self):
         output = io.StringIO()