diff --git a/src/confid/mod.rs b/src/confid/mod.rs
index 397a938..63dc290 100644
--- a/src/confid/mod.rs
+++ b/src/confid/mod.rs
@@ -21,6 +21,12 @@ pub enum ConfirmationIdError {
 }
 
 pub fn generate(installation_id: &str) -> Result<String, ConfirmationIdError> {
+    if installation_id.len() < 54 {
+        return Err(ConfirmationIdError::TooShort);
+    }
+    if installation_id.len() > 54 {
+        return Err(ConfirmationIdError::TooLarge);
+    }
     let inst_id = CString::new(installation_id).unwrap();
     let conf_id = [0u8; 49];
     let result = unsafe { black_box::generate(inst_id.as_ptr(), conf_id.as_ptr() as *mut i8) };