diff --git a/src/ifcopenshell-python/ifcopenshell/util/selector.py b/src/ifcopenshell-python/ifcopenshell/util/selector.py
index 79b2e5ebac..6d3209ac3d 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/selector.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/selector.py
@@ -18,7 +18,7 @@
 
 import re
 from collections.abc import Iterable
-from decimal import Decimal
+from decimal import Decimal, InvalidOperation
 from types import EllipsisType
 from typing import Any, Optional, Union
 
@@ -316,7 +316,13 @@ class FormatTransformer(lark.Transformer):
         return value in ("true", "1", "yes")
 
     def round(self, args):
-        value = Decimal(0.0 if args[0] == "None" else args[0] or 0.0)
+        try:
+            value = Decimal(0.0 if args[0] == "None" else args[0] or 0.0)
+        except InvalidOperation:
+            # The value is not numeric (e.g. a text property, or a value with
+            # a unit suffix like "12.5 m"). Rounding is meaningless here, so
+            # return it unchanged instead of crashing the whole expression.
+            return args[0]
         nearest = Decimal(args[1])
         result = round(value / nearest) * nearest
         if nearest % 1 == 0:
diff --git a/src/ifcopenshell-python/test/util/test_selector.py b/src/ifcopenshell-python/test/util/test_selector.py
index 3319e0df7a..485a1b886a 100644
--- a/src/ifcopenshell-python/test/util/test_selector.py
+++ b/src/ifcopenshell-python/test/util/test_selector.py
@@ -55,6 +55,9 @@ class TestFormat(test.bootstrap.IFC4):
         assert subject.format("round(123, 5)") == "125"
         assert subject.format('round("123", 5)') == "125"
         assert subject.format("round(-123, 5)") == "-125"
+        # Non-numeric values must pass through unchanged instead of crashing (#6776).
+        assert subject.format('round("Level 1", 0.01)') == "Level 1"
+        assert subject.format('round("12.5 m", 0.01)') == "12.5 m"
         assert subject.format("int(123.123)") == "123"
         assert subject.format("int(123)") == "123"
         assert subject.format("number(123)") == "123"