diff --git a/cmr/queries.py b/cmr/queries.py
index 3e4a1f9..2d91505 100644
--- a/cmr/queries.py
+++ b/cmr/queries.py
@@ -6,7 +6,7 @@
 from collections import defaultdict
 from datetime import date, datetime, timezone
 from inspect import getmembers, ismethod
-from re import search
+from re import fullmatch
 from typing import Iterable, Iterator
 
 from typing_extensions import (
@@ -228,7 +228,7 @@ def format(self, output_format: str = "json") -> Self:
 
         # check requested format against the valid format regex's
         for _format in self._valid_formats_regex:
-            if search(_format, output_format):
+            if fullmatch(_format, output_format):
                 self._format = output_format
                 return self
 
@@ -1027,7 +1027,7 @@ def __init__(self, mode: str = CMR_OPS):
         Query.__init__(self, "collections", mode)
         self.concept_id_chars = {"C"}
         self._valid_formats_regex.extend([
-            "dif", "dif10", "opendata", "umm_json", "umm_json_v[0-9]_[0-9]"
+            "dif", "dif10", "opendata", "umm_json", "umm_json_v[0-9]+_[0-9]+"
         ])
 
     def archive_center(self, center: str) -> Self:
@@ -1242,7 +1242,7 @@ def __init__(self, mode: str = CMR_OPS):
         Query.__init__(self, "tools", mode)
         self.concept_id_chars = {"T"}
         self._valid_formats_regex.extend([
-            "dif", "dif10", "opendata", "umm_json", "umm_json_v[0-9]_[0-9]"
+            "dif", "dif10", "opendata", "umm_json", "umm_json_v[0-9]+_[0-9]+"
         ])
 
     @override
@@ -1259,7 +1259,7 @@ def __init__(self, mode: str = CMR_OPS):
         Query.__init__(self, "services", mode)
         self.concept_id_chars = {"S"}
         self._valid_formats_regex.extend([
-            "dif", "dif10", "opendata", "umm_json", "umm_json_v[0-9]_[0-9]"
+            "dif", "dif10", "opendata", "umm_json", "umm_json_v[0-9]+_[0-9]+"
         ])
 
     @override
@@ -1273,7 +1273,7 @@ def __init__(self, mode: str = CMR_OPS):
         Query.__init__(self, "variables", mode)
         self.concept_id_chars = {"V"}
         self._valid_formats_regex.extend([
-            "dif", "dif10", "opendata", "umm_json", "umm_json_v[0-9]_[0-9]"
+            "dif", "dif10", "opendata", "umm_json", "umm_json_v[0-9]+_[0-9]+"
         ])
 
     def instance_format(self, format: Union[str, Sequence[str]]) -> Self:
diff --git a/tests/test_collection.py b/tests/test_collection.py
index 2edeb4f..49ea542 100644
--- a/tests/test_collection.py
+++ b/tests/test_collection.py
@@ -34,7 +34,7 @@ def test_valid_formats(self):
         formats = [
             "json", "xml", "echo10", "iso", "iso19115",
             "csv", "atom", "kml", "native", "dif", "dif10",
-            "opendata", "umm_json", "umm_json_v1_1" "umm_json_v1_9"]
+            "opendata", "umm_json", "umm_json_v1_1", "umm_json_v1_9"]
 
         for _format in formats:
             query.format(_format)
diff --git a/tests/test_format_validation.py b/tests/test_format_validation.py
new file mode 100644
index 0000000..20edbb9
--- /dev/null
+++ b/tests/test_format_validation.py
@@ -0,0 +1,18 @@
+import pytest
+
+from cmr.queries import CollectionQuery, GranuleQuery, ServiceQuery, ToolQuery, VariableQuery
+
+
+@pytest.mark.parametrize("query_type", [CollectionQuery, GranuleQuery, ServiceQuery, ToolQuery, VariableQuery])
+@pytest.mark.parametrize("output_format", ["jsonn", "not-json", "iso19116", "umm_json_v1_9suffix"])
+def test_rejects_partial_format_matches(query_type, output_format):
+    query = query_type()
+    with pytest.raises(ValueError, match="Unsupported format"):
+        query.format(output_format)
+    assert query._format == "json"
+
+
+@pytest.mark.parametrize("output_format", ["umm_json", "umm_json_v1_9", "umm_json_v1_18"])
+def test_accepts_complete_umm_versions(output_format):
+    query = CollectionQuery().format(output_format)
+    assert query._format == output_format
diff --git a/tests/test_service.py b/tests/test_service.py
index 47e1d34..e664534 100644
--- a/tests/test_service.py
+++ b/tests/test_service.py
@@ -38,7 +38,7 @@ def test_valid_formats(self):
         formats = [
             "json", "xml", "echo10", "iso", "iso19115",
             "csv", "atom", "kml", "native", "dif", "dif10",
-            "opendata", "umm_json", "umm_json_v1_1" "umm_json_v1_9"]
+            "opendata", "umm_json", "umm_json_v1_1", "umm_json_v1_9"]
 
         for _format in formats:
             query.format(_format)
diff --git a/tests/test_tool.py b/tests/test_tool.py
index 5505f18..82551d0 100644
--- a/tests/test_tool.py
+++ b/tests/test_tool.py
@@ -38,7 +38,7 @@ def test_valid_formats(self):
         formats = [
             "json", "xml", "echo10", "iso", "iso19115",
             "csv", "atom", "kml", "native", "dif", "dif10",
-            "opendata", "umm_json", "umm_json_v1_1" "umm_json_v1_9"]
+            "opendata", "umm_json", "umm_json_v1_1", "umm_json_v1_9"]
 
         for _format in formats:
             query.format(_format)
diff --git a/tests/test_variable.py b/tests/test_variable.py
index cf9fc15..efbc3e8 100644
--- a/tests/test_variable.py
+++ b/tests/test_variable.py
@@ -38,7 +38,7 @@ def test_valid_formats(self):
         formats = [
             "json", "xml", "echo10", "iso", "iso19115",
             "csv", "atom", "kml", "native", "dif", "dif10",
-            "opendata", "umm_json", "umm_json_v1_1" "umm_json_v1_9"]
+            "opendata", "umm_json", "umm_json_v1_1", "umm_json_v1_9"]
 
         for _format in formats:
             query.format(_format)