diff --git a/src/system_wrappers/interface/file_wrapper.h b/src/system_wrappers/interface/file_wrapper.h
index d8112ee6d2..71f945aee9 100644
--- a/src/system_wrappers/interface/file_wrapper.h
+++ b/src/system_wrappers/interface/file_wrapper.h
@@ -40,7 +40,8 @@ public:
 
     virtual int CloseFile() = 0;
 
-    // Limits the file size.
+    // Limits the file size to |bytes|. Writing will fail after the cap
+    // is hit. Pass zero to use an unlimited size.
     virtual int SetMaxFileSize(size_t bytes)  = 0;
 
     // Flush any pending writes.
diff --git a/src/system_wrappers/source/file_impl.cc b/src/system_wrappers/source/file_impl.cc
index 3fc913707f..c58d419168 100644
--- a/src/system_wrappers/source/file_impl.cc
+++ b/src/system_wrappers/source/file_impl.cc
@@ -232,7 +232,7 @@ int FileWrapperImpl::WriteText(const char* format, ...)
 
 bool FileWrapperImpl::Write(const void* buf, int len)
 {
-    if (!_readOnly)
+    if (_readOnly)
     {
         return false;
     }
@@ -240,7 +240,7 @@ bool FileWrapperImpl::Write(const void* buf, int len)
     if (_id != NULL)
     {
         // Check if it's time to stop writing.
-        if (_sizeInBytes + len > _maxSizeInBytes)
+        if (_maxSizeInBytes > 0 && (_sizeInBytes + len) > _maxSizeInBytes)
         {
             Flush();
             return false;