diff --git a/backend/alembic/versions/003_problem_correlation.py b/backend/alembic/versions/003_problem_correlation.py
index 8c9c02f..c760f70 100644
--- a/backend/alembic/versions/003_problem_correlation.py
+++ b/backend/alembic/versions/003_problem_correlation.py
@@ -26,15 +26,18 @@ def upgrade() -> None:
     op.create_index("ix_problems_last_seen_at", "problems", ["last_seen_at"])
 
     op.execute(
-        """
-        UPDATE problems p SET
-            fingerprint = 'h' || COALESCE(p.host_id::text, '0') || ':r' || COALESCE(p.rule_id, 'unknown'),
-            event_count = COALESCE(
-                (SELECT COUNT(*)::int FROM problem_events pe WHERE pe.problem_id = p.id),
-                1
-            ),
-            last_seen_at = COALESCE(p.updated_at, p.created_at)
-        """
+        sa.text(
+            """
+            UPDATE problems p SET
+                fingerprint = 'h' || COALESCE(p.host_id::text, '0') || chr(58) || 'r'
+                    || COALESCE(p.rule_id, 'unknown'),
+                event_count = COALESCE(
+                    (SELECT COUNT(*)::int FROM problem_events pe WHERE pe.problem_id = p.id),
+                    1
+                ),
+                last_seen_at = COALESCE(p.updated_at, p.created_at)
+            """
+        )
     )
 
     op.alter_column("problems", "fingerprint", nullable=False)