diff --git a/Userland/Libraries/LibCore/Stream.h b/Userland/Libraries/LibCore/Stream.h
index b024bebbb6..af688570f6 100644
--- a/Userland/Libraries/LibCore/Stream.h
+++ b/Userland/Libraries/LibCore/Stream.h
@@ -627,7 +627,7 @@ public:
             // user buffer.
             StringView remaining_buffer { m_buffer.span().offset(offset), maximum_offset - offset };
             for (auto candidate : candidates) {
-                if (candidate.length() > offset)
+                if (candidate.length() > remaining_buffer.length())
                     continue;
                 if (remaining_buffer.starts_with(candidate))
                     longest_match = max(longest_match, candidate.length());
@@ -640,6 +640,8 @@ public:
                 buffer_to_take.copy_to(buffer);
                 m_buffer.overwrite(0, buffer_to_shift.data(), buffer_to_shift.size());
 
+                m_buffered_size -= offset + longest_match;
+
                 return offset;
             }
         }
@@ -654,6 +656,8 @@ public:
         buffer_to_take.copy_to(buffer);
         m_buffer.overwrite(0, buffer_to_shift.data(), buffer_to_shift.size());
 
+        m_buffered_size -= readable_size;
+
         return readable_size;
     }