diff --git a/headroom/evals/memory/judge.py b/headroom/evals/memory/judge.py
index be468e844..4e711d352 100644
--- a/headroom/evals/memory/judge.py
+++ b/headroom/evals/memory/judge.py
@@ -201,7 +201,8 @@ def _parse_judge_response(text: str) -> tuple[float, str]:
         Tuple of (score, reasoning).
     """
     reasoning = ""
-    score = 3.0  # Default to middle score if parsing fails
+    score: float | None = None
+    parsed = False
 
     lines = text.strip().split("\n")
 
@@ -222,9 +223,20 @@ def _parse_judge_response(text: str) -> tuple[float, str]:
                     score = float(match.group(1))
                     # Clamp to valid range
                     score = max(1.0, min(5.0, score))
+                    parsed = True
             except ValueError:
                 logger.warning(f"Could not parse score from: {score_text}")
 
+    if not parsed:
+        # Default to a failing score so unparseable judge output doesn't
+        # silently pass downstream `judge_score >= 3.0` checks.
+        logger.warning(
+            f"Could not parse a score from judge response, defaulting to 0.0 (fail): {text!r}"
+        )
+        score = 0.0
+
+    assert score is not None
+
     # If no explicit reasoning found, use the whole text
     if not reasoning:
         reasoning = text.strip()
diff --git a/tests/test_memory_eval.py b/tests/test_memory_eval.py
index 0f57021da..d422cf1b0 100644
--- a/tests/test_memory_eval.py
+++ b/tests/test_memory_eval.py
@@ -180,6 +180,19 @@ Score: 3.5"""
         score, _ = _parse_judge_response(response)
         assert score == 1.0
 
+    def test_parse_judge_response_unparseable_defaults_to_failing_score(self):
+        """Unparseable judge output must default below the pass threshold.
+
+        Regression test for #1890: a missing/garbled "Score:" line used to
+        default to 3.0, which is exactly the `judge_score >= 3.0` pass
+        threshold in before_after.py, silently marking unparseable judge
+        responses as passing.
+        """
+        response = "The model's response looks reasonable overall."
+
+        score, _ = _parse_judge_response(response)
+        assert score < 3.0
+
     def test_simple_judge_exact_match(self):
         """Test simple judge with exact match."""
         score, reasoning = simple_judge(