diff --git a/lib/std/io/stream.c3 b/lib/std/io/stream.c3
index 962aa5e8d..cf21a4c7b 100644
--- a/lib/std/io/stream.c3
+++ b/lib/std/io/stream.c3
@@ -1,7 +1,5 @@
 module std::io;
 import std::math;
-import std::core::env;
-
 
 interface InStream
 {
@@ -36,7 +34,7 @@ fn usz? available(InStream s)
 		s.seek(curr, Seek.SET)!;
 		return len - curr;
 	}
-	return 0;
+	return ^io::UNSUPPORTED_OPERATION;
 }
 
 macro bool @is_instream(#expr) @const
@@ -90,21 +88,31 @@ macro usz? read_all(stream, char[] buffer)
 }
 
 <*
+ This function will read to the end of the stream.
+
  @require @is_instream(stream)
 *>
 macro char[]? read_fully(Allocator allocator, stream)
 {
-	usz len = available(stream)!;
-	char* data = allocator::malloc_try(allocator, len)!;
-	defer catch allocator::free(allocator, data);
-	usz read = 0;
-	while (read < len)
+	// Efficient path if it is possible to pre-allocate
+	if (try len = available(stream))
 	{
-		read += stream.read(data[read:len - read])!;
+		char* data = allocator::malloc_try(allocator, len)!;
+		defer catch allocator::free(allocator, data);
+		usz read = 0;
+		while (read < len)
+		{
+			read += stream.read(data[read:len - read])!;
+		}
+		return data[:len];
 	}
-	return data[:len];
+	ByteWriter writer;
+	writer.init(allocator);
+	copy_to(stream, &writer)!;
+	return writer.array_view();
 }
 
+
 <*
  @require @is_outstream(stream)
 *>
diff --git a/lib/std/io/stream/bytewriter.c3 b/lib/std/io/stream/bytewriter.c3
index 8a87e506c..b982894e7 100644
--- a/lib/std/io/stream/bytewriter.c3
+++ b/lib/std/io/stream/bytewriter.c3
@@ -43,6 +43,11 @@ fn void? ByteWriter.destroy(&self) @dynamic
 	*self = { };
 }
 
+fn char[] ByteWriter.array_view(self) @inline
+{
+	return self.bytes[:self.index];
+}
+
 fn String ByteWriter.str_view(&self) @inline
 {
 	return (String)self.bytes[:self.index];
@@ -91,7 +96,7 @@ fn usz? ByteWriter.read_from(&self, InStream reader) @dynamic
 	}
 	if (self.bytes.len == 0)
 	{
-		self.ensure_capacity(16)!;
+		self.ensure_capacity(256)!;
 	}
 	while (true)
 	{
diff --git a/releasenotes.md b/releasenotes.md
index e4d0d8f8a..7d71b0139 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -49,6 +49,7 @@
 - `String.replace` no longer depends on `String.split`.
 - Fix the case where `\u<unicode char>` could crash the compiler on some platforms.
 - Designated initialization with ranges would not error on overflow by 1.
+- `io::read_fully` now handles unbounded streams properly.
 
 ### Stdlib changes
 - Add `ThreadPool` join function to wait for all threads to finish in the pool without destroying the threads.
diff --git a/test/unit/stdlib/io/read_full.c3 b/test/unit/stdlib/io/read_full.c3
new file mode 100644
index 000000000..4f1864085
--- /dev/null
+++ b/test/unit/stdlib/io/read_full.c3
@@ -0,0 +1,30 @@
+module std::io @test;
+
+struct Test (InStream)
+{
+	char[] data;
+	int index;
+}
+
+fn char? Test.read_byte(&self) @dynamic
+{
+	if (self.index >= self.data.len) return io::EOF~;
+	return self.data[self.index++];
+}
+
+fn usz? Test.read(&self, char[] buffer) @dynamic
+{
+	io::printn(*self);
+	if (self.index >= self.data.len) return io::EOF~;
+	int len = min((int)self.data.len - self.index, 16);
+	buffer[:len] = self.data[self.index:len];
+	self.index += len;
+	return len;
+}
+
+fn void read_fully_stream()
+{
+	Test t = { .data = "Heokep o opewkfpewkfpoew kfopwekfop ewkf ewopfkewop fopkewfopk ewopfkewpo fkopew kfpoewk fej!" };
+	char[] data = io::read_fully(tmem, &t)!!;
+	test::eq(data, t.data);
+}