diff --git a/CHANGELOG.md b/CHANGELOG.md
index caaa28d..754197e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## [0.2.8] - Unreleased
 - Fixed bug with subtype for semantic code
 - Changed URI representation to upper case
+- Changed to disallow ISCC-ID creation from ISCC-IDs
 - Added line conversion tool
 - Updated dependencies
 
diff --git a/docs/changelog.md b/docs/changelog.md
index caaa28d..754197e 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -3,6 +3,7 @@
 ## [0.2.8] - Unreleased
 - Fixed bug with subtype for semantic code
 - Changed URI representation to upper case
+- Changed to disallow ISCC-ID creation from ISCC-IDs
 - Added line conversion tool
 - Updated dependencies
 
diff --git a/iscc_core/iscc_id.py b/iscc_core/iscc_id.py
index 9d7f661..17199fe 100644
--- a/iscc_core/iscc_id.py
+++ b/iscc_core/iscc_id.py
@@ -92,8 +92,11 @@ def soft_hash_iscc_id_v0(iscc_code, wallet, uc=0):
         digests.append(decoded[0][:1] + unpacked[0][-1][:7])
     else:
         for dec, unp in zip(decoded, unpacked):
-            if unp[0] == ic.MT.INSTANCE:
+            mt = unp[0]
+            if mt == ic.MT.INSTANCE:
                 continue
+            if mt == ic.MT.ID:
+                raise ValueError("Cannot create ISCC-ID from ISCC-ID")
             # first byte of header + first 7 bytes of body
             digests.append(dec[:1] + unp[-1][:7])
 
diff --git a/tests/test_iscc_id.py b/tests/test_iscc_id.py
index 68dc778..affd260 100644
--- a/tests/test_iscc_id.py
+++ b/tests/test_iscc_id.py
@@ -136,3 +136,27 @@ def test_iscc_id_incr_v0_raises_bad_chain_id():
     assert iscc_id == "MQAAAAAAAAAAAAAA"
     with pytest.raises(AssertionError):
         ic.iscc_id_incr_v0(iscc_id)
+
+
+def test_iscc_id_unit_types():
+    # Meta-Code 256-bits only
+    mc = ic.Code.rnd(mt=ic.MT.META, bits=256)
+    assert ic.gen_iscc_id(mc.code, 0, "a") == {"iscc": "ISCC:MAAMUFVSHK6CYVQW"}
+    assert ic.gen_iscc_id(mc.uri, 0, "a") == {"iscc": "ISCC:MAAMUFVSHK6CYVQW"}
+
+    # Meta-Code 64-bit prefix
+    mc2 = ic.encode_component(ic.MT.META, ic.ST.NONE, 0, bit_length=64, digest=mc.hash_bytes[:8])
+    assert ic.gen_iscc_id(mc2, 0, "a") == {"iscc": "ISCC:MAAMUFVSHK6CYVQW"}
+
+    cc = ic.Code.rnd(mt=ic.MT.CONTENT, bits=64)
+    assert ic.gen_iscc_id(cc.code, 0, "a") == {"iscc": "ISCC:MAAOXNCHOPSVHG2M"}
+
+    fc = ic.Code.rnd(mt=ic.MT.FLAKE, bits=64)
+    assert ic.gen_iscc_id(fc.code, 0, "a") == {"iscc": "ISCC:MAALUWZEW5VYL4FE"}
+
+
+def test_iscc_id_from_iscc_id_raises():
+    iid = ic.Code.rnd(mt=ic.MT.ID, bits=64)
+    assert iid.code == "MIAORZJBNL6L2BGD"
+    with pytest.raises(ValueError):
+        ic.gen_iscc_id(iid.code, 0, "a")