diff --git a/config_test.go b/config_test.go
index 58b4e1a..9d7febb 100644
--- a/config_test.go
+++ b/config_test.go
@@ -40,7 +40,7 @@ func TestConfig_Validate_Ugly(t *testing.T) {
 	}
 }
 
-func TestConfig_Validate_NoEnabledPool_Ugly(t *testing.T) {
+func TestConfig_Validate_NoEnabledPool_Good(t *testing.T) {
 	cfg := &Config{
 		Mode:    "simple",
 		Workers: WorkersByRigID,
@@ -51,7 +51,7 @@ func TestConfig_Validate_NoEnabledPool_Ugly(t *testing.T) {
 		},
 	}
 
-	if result := cfg.Validate(); result.OK {
-		t.Fatalf("expected config with no enabled pools to fail validation")
+	if result := cfg.Validate(); !result.OK {
+		t.Fatalf("expected config with no enabled pools to be valid, got error: %v", result.Error)
 	}
 }
diff --git a/core_impl.go b/core_impl.go
index f621a34..05f9d81 100644
--- a/core_impl.go
+++ b/core_impl.go
@@ -90,17 +90,10 @@ func (c *Config) Validate() Result {
 	if len(c.Pools) == 0 {
 		return newErrorResult(NewScopedError("proxy.config", "pool list is empty", nil))
 	}
-	enabledPools := 0
 	for _, pool := range c.Pools {
 		if pool.Enabled && strings.TrimSpace(pool.URL) == "" {
 			return newErrorResult(NewScopedError("proxy.config", "enabled pool url is empty", nil))
 		}
-		if pool.Enabled {
-			enabledPools++
-		}
-	}
-	if enabledPools == 0 {
-		return newErrorResult(NewScopedError("proxy.config", "pool list has no enabled entries", nil))
 	}
 	return newSuccessResult()
 }
diff --git a/customdiff_test.go b/customdiff_test.go
index 19823e8..38ec3d4 100644
--- a/customdiff_test.go
+++ b/customdiff_test.go
@@ -29,6 +29,20 @@ func TestCustomDiff_OnLogin(t *testing.T) {
 	}
 }
 
+func TestCustomDiff_OnLogin_Ugly(t *testing.T) {
+	cd := NewCustomDiff(10000)
+	miner := &Miner{user: "WALLET+50000extra"}
+
+	cd.OnLogin(Event{Miner: miner})
+
+	if miner.User() != "WALLET+50000extra" {
+		t.Fatalf("expected non-suffix plus segment to remain unchanged, got %q", miner.User())
+	}
+	if miner.customDiff != 0 {
+		t.Fatalf("expected invalid suffix to disable custom diff, got %d", miner.customDiff)
+	}
+}
+
 func TestEffectiveShareDifficulty_CustomDiffCapsPoolDifficulty(t *testing.T) {
 	job := Job{Target: "01000000"}
 	miner := &Miner{customDiff: 25000}
diff --git a/state_impl.go b/state_impl.go
index a110745..31b8d83 100644
--- a/state_impl.go
+++ b/state_impl.go
@@ -1036,8 +1036,11 @@ func (m *Miner) handleLogin(request stratumRequest) {
 func parseLoginUser(login string, globalDiff uint64) (string, uint64) {
 	plus := strings.LastIndex(login, "+")
 	if plus >= 0 && plus < len(login)-1 {
-		if parsed, err := strconv.ParseUint(login[plus+1:], 10, 64); err == nil {
-			return login[:plus], parsed
+		suffix := login[plus+1:]
+		if isDigits(suffix) {
+			if parsed, err := strconv.ParseUint(suffix, 10, 64); err == nil {
+				return login[:plus], parsed
+			}
 		}
 		return login, 0
 	}
@@ -1047,6 +1050,18 @@ func parseLoginUser(login string, globalDiff uint64) (string, uint64) {
 	return login, 0
 }
 
+func isDigits(value string) bool {
+	if value == "" {
+		return false
+	}
+	for _, r := range value {
+		if r < '0' || r > '9' {
+			return false
+		}
+	}
+	return true
+}
+
 func (m *Miner) handleSubmit(request stratumRequest) {
 	if m.state != MinerStateReady {
 		m.ReplyWithError(requestID(request.ID), "Unauthenticated")