diff --git a/router/src/lib.rs b/router/src/lib.rs
index ddb28848..3c9177c0 100644
--- a/router/src/lib.rs
+++ b/router/src/lib.rs
@@ -280,6 +280,31 @@ fn default_parameters() -> GenerateParameters {
     }
 }
 
+mod prompt_serde {
+    use serde::{self, Deserialize, Deserializer};
+    use serde_json::Value;
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<String, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let value = Value::deserialize(deserializer)?;
+        match value {
+            Value::String(s) => Ok(s),
+            Value::Array(arr) => arr
+                .first()
+                .and_then(|v| v.as_str())
+                .map(|s| s.to_string())
+                .ok_or_else(|| {
+                    serde::de::Error::custom("array is empty or contains non-string elements")
+                }),
+            _ => Err(serde::de::Error::custom(
+                "expected a string or an array of strings",
+            )),
+        }
+    }
+}
+
 #[derive(Clone, Deserialize, Serialize, ToSchema, Debug)]
 pub struct CompletionRequest {
     /// UNUSED
@@ -289,6 +314,7 @@ pub struct CompletionRequest {
 
     /// The prompt to generate completions for.
     #[schema(example = "What is Deep Learning?")]
+    #[serde(deserialize_with = "prompt_serde::deserialize")]
     pub prompt: String,
 
     /// The maximum number of tokens that can be generated in the chat completion.