diff --git a/headers/os/locale/MessageFormat.h b/headers/os/locale/MessageFormat.h
index 9d75c1ab3e..eeaf978c00 100644
--- a/headers/os/locale/MessageFormat.h
+++ b/headers/os/locale/MessageFormat.h
@@ -28,7 +28,7 @@ public:
 
 			status_t			InitCheck();
 
-			status_t			Format(BString& buffer, const off_t arg) const;
+			status_t			Format(BString& buffer, const int64 arg) const;
 
 private:
 			status_t			_Initialize(const icu::UnicodeString&);
diff --git a/src/kits/locale/MessageFormat.cpp b/src/kits/locale/MessageFormat.cpp
index b4dc58c325..4c66e5a08f 100644
--- a/src/kits/locale/MessageFormat.cpp
+++ b/src/kits/locale/MessageFormat.cpp
@@ -45,7 +45,7 @@ BMessageFormat::InitCheck()
 
 
 status_t
-BMessageFormat::Format(BString& output, const off_t arg) const
+BMessageFormat::Format(BString& output, const int64 arg) const
 {
 	if (fInitStatus != B_OK)
 		return fInitStatus;
@@ -54,7 +54,7 @@ BMessageFormat::Format(BString& output, const off_t arg) const
 	UErrorCode error = U_ZERO_ERROR;
 
 	Formattable arguments[] = {
-		(off_t)arg
+		(int64)arg
 	};
 
 	FieldPosition pos;