diff --git a/models/action.go b/models/action.go
index 3bc88f0063..cd722cbe7c 100644
--- a/models/action.go
+++ b/models/action.go
@@ -122,10 +122,13 @@ func (a *Action) ShortActUserName() string {
 	return base.EllipsisString(a.GetActUserName(), 20)
 }
 
-// GetDisplayName gets the action's display name based on DEFAULT_SHOW_FULL_NAME
+// GetDisplayName gets the action's display name based on DEFAULT_SHOW_FULL_NAME, or falls back to the username if it is blank.
 func (a *Action) GetDisplayName() string {
 	if setting.UI.DefaultShowFullName {
-		return a.GetActFullName()
+		trimmedFullName := strings.TrimSpace(a.GetActFullName())
+		if len(trimmedFullName) > 0 {
+			return trimmedFullName
+		}
 	}
 	return a.ShortActUserName()
 }
diff --git a/models/user.go b/models/user.go
index d8c0fcf47d..4cc14664db 100644
--- a/models/user.go
+++ b/models/user.go
@@ -712,9 +712,11 @@ func (u *User) DisplayName() string {
 // GetDisplayName returns full name if it's not empty and DEFAULT_SHOW_FULL_NAME is set,
 // returns username otherwise.
 func (u *User) GetDisplayName() string {
-	trimmed := strings.TrimSpace(u.FullName)
-	if len(trimmed) > 0 && setting.UI.DefaultShowFullName {
-		return trimmed
+	if setting.UI.DefaultShowFullName {
+		trimmed := strings.TrimSpace(u.FullName)
+		if len(trimmed) > 0 {
+			return trimmed
+		}
 	}
 	return u.Name
 }