diff --git a/guix-data-service/metrics.scm b/guix-data-service/metrics.scm
index ca1d97a..143fa7e 100644
--- a/guix-data-service/metrics.scm
+++ b/guix-data-service/metrics.scm
@@ -107,25 +107,25 @@ WHERE relname NOT LIKE 'package_derivations_by_guix_revision_range_git_branch_%'
                    last-vacuum last-autovacuum last-analyze last-autoanalyze
                    vacuum-count autovacuum-count analyze-count autoanalyze-count)
           `((name                . ,relname)
-            (seq-scan            . ,seq-scan)
-            (seq-tup-read        . ,seq-tup-read)
-            (idx-scan            . ,idx-scan)
-            (idx-tup-fetch       . ,idx-tup-fetch)
-            (n-tup-ins           . ,n-tup-ins)
-            (n-tup-upd           . ,n-tup-upd)
-            (n-tup-del           . ,n-tup-del)
-            (n-tup-hot-upd       . ,n-tup-hot-upd)
-            (n-live-tup          . ,n-live-tup)
-            (n-dead-tup          . ,n-dead-tup)
-            (n-mod-since-analyze . ,n-mod-since-analyze)
-            (last-vacuum         . ,last-vacuum)
-            (last-autovacuum     . ,last-autovacuum)
-            (last-analyze        . ,last-analyze)
-            (last-autoanalyze    . ,last-autoanalyze)
-            (vacuum-count        . ,vacuum-count)
-            (autovacuum-count    . ,autovacuum-count)
-            (analyze-count       . ,analyze-count)
-            (autoanalyze-count   . ,autoanalyze-count))))
+            (seq-scan            . ,(string->number seq-scan))
+            (seq-tup-read        . ,(string->number seq-tup-read))
+            (idx-scan            . ,(string->number idx-scan))
+            (idx-tup-fetch       . ,(string->number idx-tup-fetch))
+            (n-tup-ins           . ,(string->number n-tup-ins))
+            (n-tup-upd           . ,(string->number n-tup-upd))
+            (n-tup-del           . ,(string->number n-tup-del))
+            (n-tup-hot-upd       . ,(string->number n-tup-hot-upd))
+            (n-live-tup          . ,(string->number n-live-tup))
+            (n-dead-tup          . ,(string->number n-dead-tup))
+            (n-mod-since-analyze . ,(string->number n-mod-since-analyze))
+            (last-vacuum         . ,(string->number last-vacuum))
+            (last-autovacuum     . ,(string->number last-autovacuum))
+            (last-analyze        . ,(string->number last-analyze))
+            (last-autoanalyze    . ,(string->number last-autoanalyze))
+            (vacuum-count        . ,(string->number vacuum-count))
+            (autovacuum-count    . ,(string->number autovacuum-count))
+            (analyze-count       . ,(string->number analyze-count))
+            (autoanalyze-count   . ,(string->number autoanalyze-count)))))
        (exec-query conn query)))
 
 (define (fetch-pg-stat-user-indexes-metrics conn)
@@ -153,10 +153,10 @@ WHERE pg_stat_user_indexes.schemaname = 'guix_data_service'
       `((name          . ,indexname)
         (table-name    . ,tablename)
         (tablespace    . ,tablespace)
-        (idx-scan      . ,idx_scan)
-        (idx-tup-read  . ,idx_tup_read)
-        (idx-tup-fetch . ,idx_tup_fetch)
-        (bytes         . ,size_in_bytes))))
+        (idx-scan      . ,(string->number idx_scan))
+        (idx-tup-read  . ,(string->number idx_tup_read))
+        (idx-tup-fetch . ,(string->number idx_tup_fetch))
+        (bytes         . ,(string->number size_in_bytes)))))
    (exec-query conn query)))
 
 (define (fetch-pg-stats-metrics conn)