diff --git a/pipeline/src/base.py b/pipeline/src/base.py
index 4635395d..a3e9ed53 100644
--- a/pipeline/src/base.py
+++ b/pipeline/src/base.py
@@ -315,8 +315,6 @@ def __init__(self, value: Union[str, IRI]):
             iri = value.value
         else:
             iri = value
-        if not rfc3987.match(iri, rule="IRI"):
-            raise ValueError("Invalid IRI")
         self.value: str = iri
 
     def __eq__(self, other):
@@ -337,4 +335,9 @@ def _validate(self, ignore=None, seen=None):
         failures = defaultdict(list)
         if self.value.startswith("file") and "value" not in ignore:
             failures["value"].append("IRI points to a local file path")
+        if not rfc3987.match(self.value, rule="IRI"):
+            if rfc3987.match(self.value.replace(" ", "%20"), rule="IRI"):
+                failures["value"].append("Invalid IRI - replace spaces with '%20'")
+            else:
+                failures["value"].append("Invalid IRI")
         return failures
diff --git a/pipeline/tests/test_instantiation.py b/pipeline/tests/test_instantiation.py
index 723231a2..715eddf8 100644
--- a/pipeline/tests/test_instantiation.py
+++ b/pipeline/tests/test_instantiation.py
@@ -74,11 +74,17 @@ def test_IRI():
             assert not failures
         else:
             assert failures["value"][0] == "IRI points to a local file path"
-    invalid_iris = ["/path/to/my/file.txt"]
-    for value in invalid_iris:
-        with pytest.raises(ValueError) as exc_info:
-            iri = IRI(value)
-        assert exc_info.value.args[0] == "Invalid IRI"
+    invalid_iris = [
+        ("/path/to/my/file.txt", "Invalid IRI"),
+        ("https://example.com/path with spaces/to/my/file.txt", "Invalid IRI - replace spaces with '%20'"),
+        ("https://data-proxy.ebrains.eu/api/v1/buckets/report%.pdf", "Invalid IRI")  # lone '%' not allowed
+    ]
+    for value, expected_message in invalid_iris:
+        iri = IRI(value)
+        assert iri.value == value
+        failures = iri._validate()
+        assert len(failures["value"]) == 1
+        assert failures["value"][0] == expected_message
 
 
 def test_link():