diff --git a/openAIImages.m b/openAIImages.m
index 5be8139..91229db 100644
--- a/openAIImages.m
+++ b/openAIImages.m
@@ -91,7 +91,8 @@
                                                 mustBeLessThanOrEqual(nvp.NumImages,10)} = 1
                 nvp.Size                (1,1) string {mustBeMember(nvp.Size, ["256x256", "512x512", ...
                                                                 "1024x1024", "1792x1024", ...
-                                                                "1024x1792"])} = "1024x1024"
+                                                                "1024x1792"]), ...
+                                                    mustBeValidSize(this,nvp.Size)} = "1024x1024"
                 nvp.Quality             (1,1) string {mustBeMember(nvp.Quality,["standard", "hd"])} 
                 nvp.Style               (1,1) string {mustBeMember(nvp.Style,["vivid", "natural"])} 
             end
@@ -99,7 +100,6 @@
             endpoint = "https://api.openai.com/v1/images/generations";
 
             validatePromptSize(this.ModelName, prompt)
-            validateSizeNVP(this.ModelName, nvp.Size)
 
              params = struct("prompt",prompt,...
                 "model",this.ModelName,...
@@ -180,9 +180,9 @@
                 nvp.MaskImagePath             {mustBeValidFileType(nvp.MaskImagePath)}
                 nvp.NumImages           (1,1) {mustBePositive, mustBeInteger,...
                                                 mustBeLessThanOrEqual(nvp.NumImages,10)} = 1
-                nvp.Size                (1,1) string {mustBeMember(nvp.Size,["256x256", ...
-                                                            "512x512", ...
-                                                            "1024x1024"])} = "1024x1024"
+                nvp.Size                (1,1) string {mustBeMember(nvp.Size,...
+                                                ["256x256", "512x512","1024x1024"]), ...
+                                                mustBeValidSize(this,nvp.Size)} = "1024x1024"
             end
     
             % For now, this is only supported for "dall-e-2"
@@ -241,8 +241,9 @@
                 imagePath                     {mustBeValidFileType(imagePath)}
                 nvp.NumImages           (1,1) {mustBePositive, mustBeInteger,...
                                                 mustBeLessThanOrEqual(nvp.NumImages,10)} = 1
-                nvp.Size                (1,1) string {mustBeMember(nvp.Size,["256x256", ...
-                                                "512x512","1024x1024"])} = "1024x1024"
+                nvp.Size                (1,1) string {mustBeMember(nvp.Size,...
+                                                ["256x256", "512x512","1024x1024"]), ...
+                                                mustBeValidSize(this,nvp.Size)} = "1024x1024"
             end
 
             % For now, this is only supported for "dall-e-2"
@@ -308,20 +309,6 @@ function mustBeValidSize(this, imagesize)
 end
 end
 
-function validateSizeNVP(model, size)
-if ismember(size,["1792x1024", "1024x1792"]) && model=="dall-e-2"
-    error("llms:invalidOptionAndValueForModel", ...
-        llms.utils.errorMessageCatalog.getMessage("llms:invalidOptionAndValueForModel", ...
-        "Size", size, model));
-end
-
-if ismember(size,["256x256", "512x512"]) && model=="dall-e-3"
-    error("llms:invalidOptionAndValueForModel", ...
-        llms.utils.errorMessageCatalog.getMessage("llms:invalidOptionAndValueForModel", ...
-        "Size", size, model));
-end
-end
-
 function validatePromptSize(model, prompt)
 numChars = numel(char(prompt));
 if model=="dall-e-3"
diff --git a/tests/topenAIImages.m b/tests/topenAIImages.m
index 8eccf3f..eb7fdb5 100644
--- a/tests/topenAIImages.m
+++ b/tests/topenAIImages.m
@@ -48,9 +48,9 @@ function invalidOptionsGenerate(testCase)
             mdl = openAIImages(ApiKey="this-is-not-a-real-key", Model="dall-e-2");
             testCase.verifyError(@()generate(mdl, "cat", Quality="hd"), "llms:invalidOptionForModel")
             testCase.verifyError(@()generate(mdl, "cat", Style="natural"), "llms:invalidOptionForModel")
-            testCase.verifyError(@()generate(mdl, "cat", Size="1024x1792"), "llms:invalidOptionAndValueForModel")
+            testCase.verifyError(@()generate(mdl, "cat", Size="1024x1792"), "MATLAB:validators:mustBeMember")
             mdl = openAIImages(ApiKey="this-is-not-a-real-key", Model="dall-e-3");
-            testCase.verifyError(@()generate(mdl, "cat", Size="256x256"), "llms:invalidOptionAndValueForModel")
+            testCase.verifyError(@()generate(mdl, "cat", Size="256x256"), "MATLAB:validators:mustBeMember")
             testCase.verifyError(@()generate(mdl, "cat", NumImages=4), "llms:invalidOptionAndValueForModel")
         end
 
@@ -201,6 +201,10 @@ function testThatImageIsReturned(testCase)
             "Input",{{ "prompt" "Size" "foo" }},...
             "Error","MATLAB:validators:mustBeMember"),...
         ...
+        "InvalidSizeForModel",struct( ...
+            "Input",{{ "prompt" "Size" "1792x1024" }},...
+            "Error","MATLAB:validators:mustBeMember"),...
+        ...
         "InvalidQualityOption",struct( ...
             "Input",{{ "prompt" "Quality" "foo" }},...
             "Error","MATLAB:validators:mustBeMember"),...