diff --git a/toolbox/loader.cpp b/toolbox/loader.cpp
index 8ab5e42..8589ccb 100644
--- a/toolbox/loader.cpp
+++ b/toolbox/loader.cpp
@@ -43,6 +43,9 @@
 #include "mm.h"
 
 #include <macos/sysequ.h>
+#include <macos/tool_return.h>
+
+using MacOS::tool_return;
 
 enum {
   fsCurPerm                     = 0x00, /* open access permissions in ioPermssn */
@@ -155,7 +158,7 @@ namespace Loader {
 
 
 		// load code seg 0.
-		uint16_t LoadCode0(Segment0Info &rv)
+		tool_return<void> LoadCode0(Segment0Info &rv)
 		{
 			uint32_t rHandle;
 			uint32_t size;
@@ -208,11 +211,11 @@ namespace Loader {
 			rv.jtEnd = rv.jtStart + rv.jtSize;
 
 			// TODO -- should ReleaseResource on rHandle.
-			return 0;
+			return MacOS::noErr;
 		}
 
 		// load a standard code segment.
-		uint16_t LoadCode(uint16_t segment)
+		tool_return<void> LoadCode(uint16_t segment)
 		{
 
 			SegmentInfo si;
@@ -238,7 +241,7 @@ namespace Loader {
 
 			Segments[segment] = si;
 
-			return 0;
+			return MacOS::noErr;
 		}
 
 
@@ -247,10 +250,10 @@ namespace Loader {
 	namespace Native
 	{
 
-		uint16_t LoadFile(const std::string &path)
+		tool_return<void> LoadFile(const std::string &path)
 		{
 
-			uint16_t err;
+			tool_return<void> err;
 
 			// open the file
 			// load code seg 0
@@ -267,6 +270,7 @@ namespace Loader {
 			// load code 0.
 			Segment0Info seg0;
 			err = LoadCode0(seg0);
+			if (!err) return err;
 
 			// iterate through the jump table to get the other
 			// code segments to load
@@ -304,7 +308,7 @@ namespace Loader {
 				if (seg >= Segments.size() || Segments[seg].address == 0)
 				{
 					err = LoadCode(seg);
-					if (err) return err;
+					if (!err) return err;
 
 					const auto &p = Segments[seg];
 					if (p.farModel)
@@ -360,7 +364,7 @@ namespace Loader {
 
 
 
-			return 0;
+			return MacOS::noErr;
 		}
 
 
diff --git a/toolbox/loader.h b/toolbox/loader.h
index 0b6b63e..de9d0b5 100644
--- a/toolbox/loader.h
+++ b/toolbox/loader.h
@@ -6,11 +6,16 @@
 
 #include <cstdint>
 
+#include <macos/tool_return.h>
+
+
 namespace Loader {
 
 	typedef std::map<std::string, std::pair<uint32_t, uint32_t>> DebugNameTable;
 	namespace Native {
 
+		using MacOS::tool_return;
+
 		/*
 		 * loads the file
 		 * sets registers PC and A5.
@@ -18,7 +23,7 @@ namespace Loader {
 		 *
 		 * Dependencies: MM, RM
 		 */
-		uint16_t LoadFile(const std::string &path);
+		tool_return<void> LoadFile(const std::string &path);
 
 		// scans segments for MacsBug debug names.
 		// associates them with the start of the segment.