diff --git a/completion.go b/completion.go
index 6617e5a7..44057616 100644
--- a/completion.go
+++ b/completion.go
@@ -7,8 +7,9 @@ import (
 )
 
 var (
-	ErrCompletionUnsupportedModel   = errors.New("this model is not supported with this method, please use CreateChatCompletion client method instead") //nolint:lll
-	ErrCompletionStreamNotSupported = errors.New("streaming is not supported with this method, please use CreateCompletionStream")                      //nolint:lll
+	ErrCompletionUnsupportedModel              = errors.New("this model is not supported with this method, please use CreateChatCompletion client method instead") //nolint:lll
+	ErrCompletionStreamNotSupported            = errors.New("streaming is not supported with this method, please use CreateCompletionStream")                      //nolint:lll
+	ErrCompletionRequestPromptTypeNotSupported = errors.New("the type of CompletionRequest.Promp only supports string and []string")                               //nolint:lll
 )
 
 // GPT3 Defines the models provided by OpenAI to use when generating
@@ -77,10 +78,16 @@ func checkEndpointSupportsModel(endpoint, model string) bool {
 	return !disabledModelsForEndpoints[endpoint][model]
 }
 
+func checkPromptType(prompt any) bool {
+	_, isString := prompt.(string)
+	_, isStringSlice := prompt.([]string)
+	return isString || isStringSlice
+}
+
 // CompletionRequest represents a request structure for completion API.
 type CompletionRequest struct {
 	Model            string         `json:"model"`
-	Prompt           string         `json:"prompt,omitempty"`
+	Prompt           any            `json:"prompt,omitempty"`
 	Suffix           string         `json:"suffix,omitempty"`
 	MaxTokens        int            `json:"max_tokens,omitempty"`
 	Temperature      float32        `json:"temperature,omitempty"`
@@ -143,6 +150,11 @@ func (c *Client) CreateCompletion(
 		return
 	}
 
+	if !checkPromptType(request.Prompt) {
+		err = ErrCompletionRequestPromptTypeNotSupported
+		return
+	}
+
 	req, err := c.requestBuilder.build(ctx, http.MethodPost, c.fullURL(urlSuffix), request)
 	if err != nil {
 		return
diff --git a/completion_test.go b/completion_test.go
index ce95faf4..2e302591 100644
--- a/completion_test.go
+++ b/completion_test.go
@@ -98,14 +98,14 @@ func handleCompletionEndpoint(w http.ResponseWriter, r *http.Request) {
 		// generate a random string of length completionReq.Length
 		completionStr := strings.Repeat("a", completionReq.MaxTokens)
 		if completionReq.Echo {
-			completionStr = completionReq.Prompt + completionStr
+			completionStr = completionReq.Prompt.(string) + completionStr
 		}
 		res.Choices = append(res.Choices, CompletionChoice{
 			Text:  completionStr,
 			Index: i,
 		})
 	}
-	inputTokens := numTokens(completionReq.Prompt) * completionReq.N
+	inputTokens := numTokens(completionReq.Prompt.(string)) * completionReq.N
 	completionTokens := completionReq.MaxTokens * completionReq.N
 	res.Usage = Usage{
 		PromptTokens:     inputTokens,
diff --git a/request_builder_test.go b/request_builder_test.go
index 0f14f93f..e5b65df0 100644
--- a/request_builder_test.go
+++ b/request_builder_test.go
@@ -51,7 +51,7 @@ func TestClientReturnsRequestBuilderErrors(t *testing.T) {
 
 	ctx := context.Background()
 
-	_, err = client.CreateCompletion(ctx, CompletionRequest{})
+	_, err = client.CreateCompletion(ctx, CompletionRequest{Prompt: "testing"})
 	if !errors.Is(err, errTestRequestBuilderFailed) {
 		t.Fatalf("Did not return error when request builder failed: %v", err)
 	}
@@ -146,3 +146,27 @@ func TestClientReturnsRequestBuilderErrors(t *testing.T) {
 		t.Fatalf("Did not return error when request builder failed: %v", err)
 	}
 }
+
+func TestReturnsRequestBuilderErrorsAddtion(t *testing.T) {
+	var err error
+	ts := test.NewTestServer().OpenAITestServer()
+	ts.Start()
+	defer ts.Close()
+
+	config := DefaultConfig(test.GetTestToken())
+	config.BaseURL = ts.URL + "/v1"
+	client := NewClientWithConfig(config)
+	client.requestBuilder = &failingRequestBuilder{}
+
+	ctx := context.Background()
+
+	_, err = client.CreateCompletion(ctx, CompletionRequest{Prompt: 1})
+	if !errors.Is(err, ErrCompletionRequestPromptTypeNotSupported) {
+		t.Fatalf("Did not return error when request builder failed: %v", err)
+	}
+
+	_, err = client.CreateCompletionStream(ctx, CompletionRequest{Prompt: 1})
+	if !errors.Is(err, ErrCompletionRequestPromptTypeNotSupported) {
+		t.Fatalf("Did not return error when request builder failed: %v", err)
+	}
+}
diff --git a/stream.go b/stream.go
index 944546a6..64688cdc 100644
--- a/stream.go
+++ b/stream.go
@@ -28,6 +28,11 @@ func (c *Client) CreateCompletionStream(
 		return
 	}
 
+	if !checkPromptType(request.Prompt) {
+		err = ErrCompletionRequestPromptTypeNotSupported
+		return
+	}
+
 	request.Stream = true
 	req, err := c.newStreamRequest(ctx, "POST", urlSuffix, request)
 	if err != nil {