diff --git a/api/client-server/administrative_contact.yaml b/api/client-server/administrative_contact.yaml
index f0a86762..4c1ea2e7 100644
--- a/api/client-server/administrative_contact.yaml
+++ b/api/client-server/administrative_contact.yaml
@@ -314,7 +314,7 @@ paths:
                 required: ['id_server']
       responses:
         200:
-          description: A SMS message was sent to the given phone number.
+          description: An SMS message was sent to the given phone number.
           schema:
             $ref: "definitions/sid.yaml"
         403:
diff --git a/api/client-server/registration.yaml b/api/client-server/registration.yaml
index c892b08d..00334434 100644
--- a/api/client-server/registration.yaml
+++ b/api/client-server/registration.yaml
@@ -300,7 +300,7 @@ paths:
       responses:
         200:
           description: |-
-            A SMS message has been sent to the specified phone number. Note
+            An SMS message has been sent to the specified phone number. Note
             that this may be an SMS message containing the validation token or
             it may be informing the user of an error.
           schema:
@@ -501,7 +501,7 @@ paths:
                 required: ['id_server']
       responses:
         200:
-          description: A SMS message was sent to the given phone number.
+          description: An SMS message was sent to the given phone number.
           schema:
             $ref: "definitions/sid.yaml"
         403: