diff --git a/vm/os-genunix.h b/vm/os-genunix.h
index 9a00758c8a..7afc68998d 100644
--- a/vm/os-genunix.h
+++ b/vm/os-genunix.h
@@ -1,6 +1,5 @@
 #define DLLEXPORT
 #define NULL_DLL NULL
-#define FSEEK fseeko
 
 void c_to_factor_toplevel(CELL quot);
 void init_signals(void);
diff --git a/vm/os-unix.h b/vm/os-unix.h
index d2f34b4bc4..35abfee41c 100755
--- a/vm/os-unix.h
+++ b/vm/os-unix.h
@@ -23,6 +23,8 @@ typedef char F_SYMBOL;
 #define STRNCMP strncmp
 #define STRDUP strdup
 
+#define FSEEK fseeko
+
 #define FIXNUM_FORMAT "%ld"
 #define CELL_FORMAT "%lu"
 #define CELL_HEX_FORMAT "%lx"