diff --git a/generate/math_roundtrip.py b/generate/math_roundtrip.py
index a03985f3..5ec361f3 100644
--- a/generate/math_roundtrip.py
+++ b/generate/math_roundtrip.py
@@ -293,6 +293,13 @@ def _unit_grounds(
     if _token_in(unit_token, haystack_tokens):
         return True
     lower = unit_token.lower()
+    # Multi-word units (e.g. "Pokemon cards", "stop signs") ground when
+    # every component appears as a word token in source. Conjunctive by
+    # design — a missing component means the unit cannot be reconstructed
+    # from the source, which preserves wrong=0.
+    parts = lower.split()
+    if len(parts) > 1 and all(p in haystack_tokens for p in parts):
+        return True
     if lower in ("cent", "cents"):
         if "$" in source_span or "¢" in source_span:
             return True
diff --git a/tests/test_math_roundtrip.py b/tests/test_math_roundtrip.py
index 92b9bfb8..df1da6fd 100644
--- a/tests/test_math_roundtrip.py
+++ b/tests/test_math_roundtrip.py
@@ -338,6 +338,48 @@ class TestNumberGrounding:
         assert roundtrip_admissible(c)
 
 
+class TestMultiWordUnitGrounding:
+    """Multi-word units (e.g. 'Pokemon cards') ground when every
+    component word appears in source. Conjunctive — missing one
+    component refuses, preserving wrong=0."""
+
+    def test_two_word_unit_grounds_when_both_components_present(self) -> None:
+        c = CandidateOperation(
+            op=Operation(actor="Nicole", kind="add",
+                         operand=Quantity(value=400, unit="Pokemon cards")),
+            source_span="Nicole collected 400 Pokemon cards.",
+            matched_verb="collected",
+            matched_value_token="400",
+            matched_unit_token="Pokemon cards",
+            matched_actor_token="Nicole",
+        )
+        assert roundtrip_admissible(c)
+
+    def test_two_word_unit_refuses_when_one_component_missing(self) -> None:
+        c = CandidateOperation(
+            op=Operation(actor="Nicole", kind="add",
+                         operand=Quantity(value=400, unit="Pokemon cards")),
+            source_span="Nicole collected 400 cards.",  # 'Pokemon' missing
+            matched_verb="collected",
+            matched_value_token="400",
+            matched_unit_token="Pokemon cards",
+            matched_actor_token="Nicole",
+        )
+        assert not roundtrip_admissible(c)
+
+    def test_single_word_unit_unaffected(self) -> None:
+        c = CandidateOperation(
+            op=Operation(actor="Sam", kind="add",
+                         operand=Quantity(value=3, unit="apples")),
+            source_span="Sam buys 3 apples.",
+            matched_verb="buys",
+            matched_value_token="3",
+            matched_unit_token="apples",
+            matched_actor_token="Sam",
+        )
+        assert roundtrip_admissible(c)
+
+
 # ---------------------------------------------------------------------------
 # Constructor validation — illegal CandidateOperation states are
 # refused at construction (not at filter time).