diff --git a/worker-sys/src/types/r2/range.rs b/worker-sys/src/types/r2/range.rs
index 7ec2dfc1..8115c5e3 100644
--- a/worker-sys/src/types/r2/range.rs
+++ b/worker-sys/src/types/r2/range.rs
@@ -3,7 +3,7 @@ use wasm_bindgen::prelude::*;
 #[wasm_bindgen]
 #[derive(Debug, Clone)]
 pub struct R2Range {
-    pub offset: Option<u32>,
-    pub length: Option<u32>,
-    pub suffix: Option<u32>,
+    pub offset: Option<f64>,
+    pub length: Option<f64>,
+    pub suffix: Option<f64>,
 }
diff --git a/worker/src/r2/builder.rs b/worker/src/r2/builder.rs
index d1fab00b..df8bce32 100644
--- a/worker/src/r2/builder.rs
+++ b/worker/src/r2/builder.rs
@@ -93,34 +93,48 @@ impl From<Conditional> for JsObject {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum Range {
-    OffsetWithLength { offset: u32, length: u32 },
-    OffsetWithOptionalLength { offset: u32, length: Option<u32> },
-    OptionalOffsetWithLength { offset: Option<u32>, length: u32 },
-    Suffix { suffix: u32 },
+    /// Read `length` bytes starting at `offset`.
+    OffsetWithLength { offset: u64, length: u64 },
+    /// Read from `offset` to the end of the object.
+    OffsetToEnd { offset: u64 },
+    /// Read `length` bytes starting at the beginning of the object.
+    Prefix { length: u64 },
+    /// Read `suffix` bytes from the end of the object.
+    Suffix { suffix: u64 },
+}
+
+const MAX_SAFE_INTEGER: u64 = js_sys::Number::MAX_SAFE_INTEGER as u64;
+
+fn check_range_precision(value: u64) -> f64 {
+    assert!(
+        value <= MAX_SAFE_INTEGER,
+        "Integer precision loss when converting to JavaScript number"
+    );
+    value as f64
 }
 
 impl From<Range> for JsObject {
     fn from(val: Range) -> Self {
         match val {
             Range::OffsetWithLength { offset, length } => js_object! {
-                "offset" => Some(offset),
-                "length" => Some(length),
+                "offset" => Some(check_range_precision(offset)),
+                "length" => Some(check_range_precision(length)),
                 "suffix" => JsValue::UNDEFINED,
             },
-            Range::OffsetWithOptionalLength { offset, length } => js_object! {
-                "offset" => Some(offset),
-                "length" => length,
+            Range::OffsetToEnd { offset } => js_object! {
+                "offset" => Some(check_range_precision(offset)),
+                "length" => JsValue::UNDEFINED,
                 "suffix" => JsValue::UNDEFINED,
             },
-            Range::OptionalOffsetWithLength { offset, length } => js_object! {
-                "offset" => offset,
-                "length" => Some(length),
+            Range::Prefix { length } => js_object! {
+                "offset" => JsValue::UNDEFINED,
+                "length" => Some(check_range_precision(length)),
                 "suffix" => JsValue::UNDEFINED,
             },
             Range::Suffix { suffix } => js_object! {
                 "offset" => JsValue::UNDEFINED,
                 "length" => JsValue::UNDEFINED,
-                "suffix" => Some(suffix),
+                "suffix" => Some(check_range_precision(suffix)),
             },
         }
     }
@@ -131,16 +145,19 @@ impl TryFrom<R2RangeSys> for Range {
 
     fn try_from(val: R2RangeSys) -> Result<Self> {
         Ok(match (val.offset, val.length, val.suffix) {
-            (Some(offset), Some(length), None) => Self::OffsetWithLength { offset, length },
-            (Some(offset), None, None) => Self::OffsetWithOptionalLength {
-                offset,
-                length: None,
+            (Some(offset), Some(length), None) => Self::OffsetWithLength {
+                offset: offset.round() as u64,
+                length: length.round() as u64,
+            },
+            (Some(offset), None, None) => Self::OffsetToEnd {
+                offset: offset.round() as u64,
+            },
+            (None, Some(length), None) => Self::Prefix {
+                length: length.round() as u64,
             },
-            (None, Some(length), None) => Self::OptionalOffsetWithLength {
-                offset: None,
-                length,
+            (None, None, Some(suffix)) => Self::Suffix {
+                suffix: suffix.round() as u64,
             },
-            (None, None, Some(suffix)) => Self::Suffix { suffix },
             _ => return Err(Error::JsError("invalid range".into())),
         })
     }