diff --git a/pkg/controller/account/age_gate.go b/pkg/controller/account/age_gate.go
index 37c1bdd..2a78851 100644
--- a/pkg/controller/account/age_gate.go
+++ b/pkg/controller/account/age_gate.go
@@ -28,6 +28,12 @@ func AgeGate() http.HandlerFunc {
 			return
 		}
 
+		// If we have already set our age, don't allow changing it.
+		if !user.Birthdate.IsZero() {
+			templates.NotFoundPage(w, r)
+			return
+		}
+
 		// Are we POSTing?
 		if r.Method == http.MethodPost {
 			var (
diff --git a/pkg/controller/account/settings.go b/pkg/controller/account/settings.go
index c9e808f..bc12891 100644
--- a/pkg/controller/account/settings.go
+++ b/pkg/controller/account/settings.go
@@ -59,20 +59,24 @@ func Settings() http.HandlerFunc {
 
 				// Set user attributes.
 				user.Name = &displayName
-				if len(dob) > 0 {
-					if birthdate, err := time.Parse("2006-01-02", dob); err != nil {
-						session.FlashError(w, r, "Incorrect format for birthdate; should be in yyyy-mm-dd format but got: %s", dob)
+
+				// Birthdate, now required.
+				if birthdate, err := time.Parse("2006-01-02", dob); err != nil {
+					session.FlashError(w, r, "Incorrect format for birthdate; should be in yyyy-mm-dd format but got: %s", dob)
+				} else {
+					// Validate birthdate is at least age 18.
+					if utility.Age(birthdate) < 18 {
+						session.FlashError(w, r, "Invalid birthdate: you must be at least 18 years old to use this site.")
+						templates.Redirect(w, r.URL.Path)
+						return
+					}
+
+					// The user isn't allowed to change it on their own, even if they edit the form to remove the readonly value.
+					if !user.Birthdate.IsZero() && user.Birthdate.Format("2006-01-02") != dob {
+						session.FlashError(w, r, "Please contact support if you want to change your birthdate.")
 					} else {
-						// Validate birthdate is at least age 18.
-						if utility.Age(birthdate) < 18 {
-							session.FlashError(w, r, "Invalid birthdate: you must be at least 18 years old to use this site.")
-							templates.Redirect(w, r.URL.Path)
-							return
-						}
 						user.Birthdate = birthdate
 					}
-				} else {
-					user.Birthdate = time.Time{}
 				}
 
 				// Set profile attributes.