diff --git a/ezsnmp/helpers.py b/ezsnmp/helpers.py
index 0c32d617..2f749082 100644
--- a/ezsnmp/helpers.py
+++ b/ezsnmp/helpers.py
@@ -3,6 +3,8 @@
 import re
 
 # This regular expression is used to extract the index from an OID
+# We attempt to extract the index from an OID (e.g. sysDescr.0
+# or .iso.org.dod.internet.mgmt.mib-2.system.sysContact.0)
 OID_INDEX_RE = re.compile(
     r"""(
             \.?\d+(?:\.\d+)*              # numeric OID
@@ -16,6 +18,10 @@
     re.VERBOSE,
 )
 
+# This regular expression takes something like 'SNMPv2::mib-2.17.7.1.4.3.1.2.300'
+# and splits it into 'SNMPv2::mib-2' and '17.7.1.4.3.1.2.300'
+OID_INDEX_RE2 = re.compile(r"^([^\.]+::[^\.]+)\.(.*)$")
+
 
 def normalize_oid(oid, oid_index=None):
     """
@@ -27,10 +33,17 @@ def normalize_oid(oid, oid_index=None):
 
     # Determine the OID index from the OID if not specified
     if oid_index is None and oid is not None:
-        # We attempt to extract the index from an OID (e.g. sysDescr.0
-        # or .iso.org.dod.internet.mgmt.mib-2.system.sysContact.0)
-        match = OID_INDEX_RE.match(oid)
-        if match:
-            oid, oid_index = match.group(1, 2)
+        first_match = OID_INDEX_RE.match(oid)
+        second_match = OID_INDEX_RE2.match(oid)
+
+        if second_match:
+            oid, oid_index = second_match.group(1, 2)
+
+        elif first_match:
+            oid, oid_index = first_match.group(1, 2)
+
+        elif oid == ".":
+            oid = "."
+            oid_index = ""
 
     return oid, oid_index
diff --git a/tests/test_helpers.py b/tests/test_helpers.py
index 070fd1b3..9ba15edd 100644
--- a/tests/test_helpers.py
+++ b/tests/test_helpers.py
@@ -3,12 +3,42 @@
 from ezsnmp.helpers import normalize_oid
 
 
+def test_normalize_oid_just_iso():
+    oid, oid_index = normalize_oid("oid")
+    assert oid == "oid"
+    assert oid_index == ""
+
+
+def test_normalize_oid_just_period():
+    oid, oid_index = normalize_oid(".")
+    assert oid == "."
+    assert oid_index == ""
+
+
 def test_normalize_oid_regular():
     oid, oid_index = normalize_oid("sysContact.0")
     assert oid == "sysContact"
     assert oid_index == "0"
 
 
+def test_normalize_oid_regular_2():
+    oid, oid_index = normalize_oid("SNMPv2::mib-2.17.7.1.4.3.1.2.300")
+    assert oid == "SNMPv2::mib-2"
+    assert oid_index == "17.7.1.4.3.1.2.300"
+
+
+def test_normalize_oid_regular_3():
+    oid, oid_index = normalize_oid("nsCacheTimeout.1.3.6.1.2.1.2")
+    assert oid == "nsCacheTimeout"
+    assert oid_index == "1.3.6.1.2.1.2"
+
+
+def test_normalize_oid_regular_4():
+    oid, oid_index = normalize_oid("iso.3.6.1.2.1.31.1.1.1.1.5035")
+    assert oid == "iso"
+    assert oid_index == "3.6.1.2.1.31.1.1.1.1.5035"
+
+
 def test_normalize_oid_numeric():
     oid, oid_index = normalize_oid(".1.3.6.1.2.1.1.1.0")
     assert oid == ".1.3.6.1.2.1.1.1.0"