diff --git a/pkgs/servers/sql/postgresql/ext/pg_byteamagic.nix b/pkgs/servers/sql/postgresql/ext/pg_byteamagic.nix
index 8de8850d04eb..83bccbdf5cfa 100644
--- a/pkgs/servers/sql/postgresql/ext/pg_byteamagic.nix
+++ b/pkgs/servers/sql/postgresql/ext/pg_byteamagic.nix
@@ -29,6 +29,13 @@ postgresqlBuildExtension (finalAttrs: {
         CREATE EXTENSION byteamagic;
         SELECT byteamagic_mime('test');
       '';
+      asserts = [
+        {
+          query = "SELECT byteamagic_mime('test')";
+          expected = "'text/plain'";
+          description = "`byteamagic_mime(...) should return proper mimetype.";
+        }
+      ];
     };
   };