diff --git a/.changelog/3786.txt b/.changelog/3786.txt
new file mode 100644
index 00000000000..94427bbbacf
--- /dev/null
+++ b/.changelog/3786.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+sourcerepo: fixed perma-diff in `google_sourcerepo_repository`
+```
diff --git a/google/resource_source_repo_repository.go b/google/resource_source_repo_repository.go
index 9f963d36823..721eff7983a 100644
--- a/google/resource_source_repo_repository.go
+++ b/google/resource_source_repo_repository.go
@@ -15,6 +15,7 @@
 package google
 
 import (
+	"bytes"
 	"fmt"
 	"log"
 	"reflect"
@@ -22,10 +23,28 @@ import (
 	"strings"
 	"time"
 
+	"github.com/hashicorp/terraform-plugin-sdk/helper/hashcode"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/validation"
 )
 
+func resourceSourceRepoRepositoryPubSubConfigsHash(v interface{}) int {
+	if v == nil {
+		return 0
+	}
+
+	var buf bytes.Buffer
+	m := v.(map[string]interface{})
+
+	buf.WriteString(fmt.Sprintf("%s-", GetResourceNameFromSelfLink(m["topic"].(string))))
+	buf.WriteString(fmt.Sprintf("%s-", m["message_format"].(string)))
+	if v, ok := m["service_account_email"]; ok {
+		buf.WriteString(fmt.Sprintf("%s-", v.(string)))
+	}
+
+	return hashcode.String(buf.String())
+}
+
 func resourceSourceRepoRepository() *schema.Resource {
 	return &schema.Resource{
 		Create: resourceSourceRepoRepositoryCreate,
@@ -81,6 +100,7 @@ If unspecified, it defaults to the compute engine default service account.`,
 						},
 					},
 				},
+				Set: resourceSourceRepoRepositoryPubSubConfigsHash,
 			},
 			"size": {
 				Type:        schema.TypeInt,