diff --git a/headers/private/storage/OffsetFile.h b/headers/private/storage/OffsetFile.h
index 35cab07d91..4f375b7cc0 100644
--- a/headers/private/storage/OffsetFile.h
+++ b/headers/private/storage/OffsetFile.h
@@ -49,7 +49,7 @@ public:
 	off_t Position() const;
 
 	status_t SetSize(off_t size);
-	status_t GetSize(off_t *size);
+	status_t GetSize(off_t *size) const;
 
 	off_t Offset() const;
 
diff --git a/src/kits/storage/OffsetFile.cpp b/src/kits/storage/OffsetFile.cpp
index 10e41b7e15..2deec8399d 100644
--- a/src/kits/storage/OffsetFile.cpp
+++ b/src/kits/storage/OffsetFile.cpp
@@ -145,7 +145,7 @@ OffsetFile::SetSize(off_t size)
 
 // GetSize
 status_t
-OffsetFile::GetSize(off_t *size)
+OffsetFile::GetSize(off_t *size) const
 {
 	status_t error = (size ? B_OK : B_BAD_VALUE );
 	if (error == B_OK)