diff --git a/agent/service_manager.go b/agent/service_manager.go
index 2c0fc2f2d..29808580e 100644
--- a/agent/service_manager.go
+++ b/agent/service_manager.go
@@ -384,7 +384,7 @@ func mergeServiceConfig(defaults *structs.ServiceConfigResponse, service *struct
 	remoteUpstreams := make(map[structs.ServiceID]structs.Upstream)
 
 	for _, us := range defaults.UpstreamIDConfigs {
-		parsed, err := structs.ParseUpstreamConfig(us.Config)
+		parsed, err := structs.ParseUpstreamConfigNoDefaults(us.Config)
 		if err != nil {
 			return nil, fmt.Errorf("failed to parse upstream config map for %s: %v", us.Upstream.String(), err)
 		}
diff --git a/agent/structs/config_entry.go b/agent/structs/config_entry.go
index ef6c8c781..c2427dfa9 100644
--- a/agent/structs/config_entry.go
+++ b/agent/structs/config_entry.go
@@ -701,8 +701,8 @@ func (cfg UpstreamConfig) MergeInto(dst map[string]interface{}) {
 func (cfg *UpstreamConfig) Normalize() {
 	cfg.Protocol = strings.ToLower(cfg.Protocol)
 
-	if cfg.ConnectTimeoutMs < 1 {
-		cfg.ConnectTimeoutMs = 5000
+	if cfg.ConnectTimeoutMs < 0 {
+		cfg.ConnectTimeoutMs = 0
 	}
 }
 
@@ -744,6 +744,8 @@ func ParseUpstreamConfigNoDefaults(m map[string]interface{}) (UpstreamConfig, er
 	}
 
 	err = decoder.Decode(m)
+	cfg.Normalize()
+
 	return cfg, err
 }
 
@@ -753,12 +755,13 @@ func ParseUpstreamConfigNoDefaults(m map[string]interface{}) (UpstreamConfig, er
 func ParseUpstreamConfig(m map[string]interface{}) (UpstreamConfig, error) {
 	cfg, err := ParseUpstreamConfigNoDefaults(m)
 
-	cfg.Normalize()
-
 	// Set default (even if error is returned)
 	if cfg.Protocol == "" {
 		cfg.Protocol = "tcp"
 	}
+	if cfg.ConnectTimeoutMs == 0 {
+		cfg.ConnectTimeoutMs = 5000
+	}
 
 	return cfg, err
 }
diff --git a/agent/structs/config_entry_test.go b/agent/structs/config_entry_test.go
index 97bc1c972..523cab002 100644
--- a/agent/structs/config_entry_test.go
+++ b/agent/structs/config_entry_test.go
@@ -1572,14 +1572,14 @@ func TestServiceConfigEntry_Normalize(t *testing.T) {
 					UpstreamConfigs: map[string]*UpstreamConfig{
 						"redis": {
 							Protocol:         "tcp",
-							ConnectTimeoutMs: 5000,
+							ConnectTimeoutMs: 0,
 						},
 						"memcached": {
-							ConnectTimeoutMs: 5000,
+							ConnectTimeoutMs: 0,
 						},
 					},
 					UpstreamDefaults: &UpstreamConfig{
-						ConnectTimeoutMs: 5000,
+						ConnectTimeoutMs: 0,
 					},
 				},
 			},
@@ -1751,6 +1751,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 			input: nil,
 			want: UpstreamConfig{
 				ConnectTimeoutMs: 5000,
+				Protocol:         "tcp",
 			},
 		},
 		{
@@ -1758,6 +1759,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 			input: map[string]interface{}{},
 			want: UpstreamConfig{
 				ConnectTimeoutMs: 5000,
+				Protocol:         "tcp",
 			},
 		},
 		{
@@ -1768,6 +1770,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 			},
 			want: UpstreamConfig{
 				ConnectTimeoutMs: 5000,
+				Protocol:         "tcp",
 			},
 		},
 		{
@@ -1787,6 +1790,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 			},
 			want: UpstreamConfig{
 				ConnectTimeoutMs: 1000,
+				Protocol:         "tcp",
 			},
 		},
 		{
@@ -1796,6 +1800,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 			},
 			want: UpstreamConfig{
 				ConnectTimeoutMs: 1000,
+				Protocol:         "tcp",
 			},
 		},
 		{
@@ -1805,6 +1810,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 			},
 			want: UpstreamConfig{
 				ConnectTimeoutMs: 1000,
+				Protocol:         "tcp",
 			},
 		},
 		{
@@ -1823,6 +1829,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 					MaxPendingRequests:    intPointer(60),
 					MaxConcurrentRequests: intPointer(70),
 				},
+				Protocol: "tcp",
 			},
 		},
 		{
@@ -1841,6 +1848,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 					MaxPendingRequests:    intPointer(0),
 					MaxConcurrentRequests: intPointer(0),
 				},
+				Protocol: "tcp",
 			},
 		},
 		{
@@ -1857,6 +1865,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 					Interval:    22 * time.Second,
 					MaxFailures: 7,
 				},
+				Protocol: "tcp",
 			},
 		},
 		{
@@ -1871,6 +1880,7 @@ func TestParseUpstreamConfig(t *testing.T) {
 				MeshGateway: MeshGatewayConfig{
 					Mode: MeshGatewayModeRemote,
 				},
+				Protocol: "tcp",
 			},
 		},
 	}