diff --git a/payjoin/src/uri/url_ext.rs b/payjoin/src/uri/url_ext.rs
index d1f42def..21a4cb96 100644
--- a/payjoin/src/uri/url_ext.rs
+++ b/payjoin/src/uri/url_ext.rs
@@ -1,4 +1,4 @@
-use std::borrow::Cow;
+use std::str::FromStr;
 
 use percent_encoding::{AsciiSet, PercentDecodeError, CONTROLS};
 use url::Url;
@@ -19,96 +19,79 @@ const BIP21_CONFLICTING: &AsciiSet = &CONTROLS.add(b'=').add(b'&');
 impl UrlExt for Url {
     /// Retrieve the ohttp parameter from the URL fragment
     fn ohttp(&self) -> Result<Option<OhttpKeys>, PercentDecodeError> {
-        use std::str::FromStr;
-        if let Some(fragment) = self.fragment() {
-            let decoded_fragment =
-                percent_encoding::percent_decode_str(fragment)?.decode_utf8_lossy();
-            for param in decoded_fragment.split('&') {
-                if let Some(value) = param.strip_prefix("ohttp=") {
-                    let ohttp = Cow::from(value);
-                    return Ok(OhttpKeys::from_str(&ohttp).ok());
-                }
-            }
-        }
-        Ok(None)
+        get_param(self, "ohttp=", |value| OhttpKeys::from_str(value).ok())
     }
 
     /// Set the ohttp parameter in the URL fragment
     fn set_ohttp(&mut self, ohttp: Option<OhttpKeys>) -> Result<(), PercentDecodeError> {
-        let fragment = self.fragment().unwrap_or("").to_string();
-        let mut fragment =
-            percent_encoding::percent_decode_str(&fragment)?.decode_utf8_lossy().to_string();
-        if let Some(start) = fragment.find("ohttp=") {
-            let end = fragment[start..].find('&').map_or(fragment.len(), |i| start + i);
-            fragment.replace_range(start..end, "");
-            if fragment.ends_with('&') {
-                fragment.pop();
-            }
-        }
-        if let Some(ohttp) = ohttp {
-            let new_ohttp = format!("ohttp={}", ohttp);
-            if !fragment.is_empty() {
-                fragment.push('&');
-            }
-            fragment.push_str(&new_ohttp);
-        }
-        let encoded_fragment =
-            percent_encoding::utf8_percent_encode(&fragment, BIP21_CONFLICTING).to_string();
-        self.set_fragment(if encoded_fragment.is_empty() { None } else { Some(&encoded_fragment) });
-        Ok(())
+        set_param(self, "ohttp=", ohttp.map(|o| o.to_string()))
     }
 
     /// Retrieve the exp parameter from the URL fragment
     fn exp(&self) -> Result<Option<std::time::SystemTime>, PercentDecodeError> {
-        if let Some(fragment) = self.fragment() {
-            let decoded_fragment =
-                percent_encoding::percent_decode_str(fragment)?.decode_utf8_lossy();
-            for param in decoded_fragment.split('&') {
-                if let Some(value) = param.strip_prefix("exp=") {
-                    if let Ok(timestamp) = value.parse::<u64>() {
-                        return Ok(Some(
-                            std::time::UNIX_EPOCH + std::time::Duration::from_secs(timestamp),
-                        ));
-                    }
-                }
-            }
-        }
-        Ok(None)
+        get_param(self, "exp=", |value| {
+            value
+                .parse::<u64>()
+                .ok()
+                .map(|timestamp| std::time::UNIX_EPOCH + std::time::Duration::from_secs(timestamp))
+        })
     }
 
     /// Set the exp parameter in the URL fragment
     fn set_exp(&mut self, exp: Option<std::time::SystemTime>) -> Result<(), PercentDecodeError> {
-        let fragment = self.fragment().unwrap_or("").to_string();
-        let mut fragment =
-            percent_encoding::percent_decode_str(&fragment)?.decode_utf8_lossy().to_string();
-        if let Some(start) = fragment.find("exp=") {
-            let end = fragment[start..].find('&').map_or(fragment.len(), |i| start + i);
-            fragment.replace_range(start..end, "");
-            if fragment.ends_with('&') {
-                fragment.pop();
+        let exp_str = exp.map(|e| {
+            match e.duration_since(std::time::UNIX_EPOCH) {
+                Ok(duration) => duration.as_secs().to_string(),
+                Err(_) => "0".to_string(), // Handle times before Unix epoch by setting to "0"
             }
-        }
-        if let Some(exp) = exp {
-            let timestamp = exp.duration_since(std::time::UNIX_EPOCH).unwrap().as_secs();
-            let new_exp = format!("exp={}", timestamp);
-            if !fragment.is_empty() {
-                fragment.push('&');
+        });
+        set_param(self, "exp=", exp_str)
+    }
+}
+
+fn get_param<F, T>(url: &Url, prefix: &str, parse: F) -> Result<Option<T>, PercentDecodeError>
+where
+    F: Fn(&str) -> Option<T>,
+{
+    if let Some(fragment) = url.fragment() {
+        let decoded_fragment = percent_encoding::percent_decode_str(fragment)?.decode_utf8_lossy();
+        for param in decoded_fragment.split('&') {
+            if let Some(value) = param.strip_prefix(prefix) {
+                return Ok(parse(value));
             }
-            fragment.push_str(&new_exp);
         }
-        let encoded_fragment =
-            percent_encoding::utf8_percent_encode(&fragment, BIP21_CONFLICTING).to_string();
-        self.set_fragment(if encoded_fragment.is_empty() { None } else { Some(&encoded_fragment) });
-        Ok(())
     }
+    Ok(None)
 }
 
-#[cfg(test)]
-mod tests {
-    use std::str::FromStr;
+fn set_param(url: &mut Url, prefix: &str, value: Option<String>) -> Result<(), PercentDecodeError> {
+    let fragment = url.fragment().unwrap_or("");
+    let mut fragment = percent_encoding::percent_decode_str(fragment)?.decode_utf8_lossy();
 
-    use url::Url;
+    if let Some(start) = fragment.find(prefix) {
+        let end = fragment[start..].find('&').map_or(fragment.len(), |i| start + i);
+        fragment.to_mut().replace_range(start..end, "");
+        if fragment.ends_with('&') {
+            fragment.to_mut().pop();
+        }
+    }
 
+    if let Some(value) = value {
+        let new_param = format!("{}{}", prefix, value);
+        if !fragment.is_empty() {
+            fragment.to_mut().push('&');
+        }
+        fragment.to_mut().push_str(&new_param);
+    }
+
+    let encoded_fragment =
+        percent_encoding::utf8_percent_encode(&fragment, BIP21_CONFLICTING).to_string();
+    url.set_fragment(if encoded_fragment.is_empty() { None } else { Some(&encoded_fragment) });
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
     use super::*;
     use crate::{Uri, UriExt};