diff --git a/src/DiskImage.cpp b/src/DiskImage.cpp
index 8f8c402..cf3fb8d 100644
--- a/src/DiskImage.cpp
+++ b/src/DiskImage.cpp
@@ -240,7 +240,7 @@ bool DiskImage::OpenD64(const FILINFO* fileInfo, unsigned char* diskImage, unsig
 			break;
 
 		default:  // non-standard images, attempt to load anyway
-			last_track = 40;
+			last_track = MAX_TRACK_D64;
 			break;
 	}
 
diff --git a/src/gcr.h b/src/gcr.h
index bf090a1..646bbc8 100644
--- a/src/gcr.h
+++ b/src/gcr.h
@@ -28,9 +28,9 @@
 
 /* D64 constants */
 #define BLOCKSONDISK (17*21 + 7*19 + 6*18 + 5*17)
-#define BLOCKSEXTRA (5*17)
+#define BLOCKSEXTRA (5*17 + 2*17)
 #define MAXBLOCKSONDISK (BLOCKSONDISK+BLOCKSEXTRA)
-#define MAX_TRACK_D64 40
+#define MAX_TRACK_D64 42
 
 /* G64 constants (only needed for current VICE support */
 #define G64_TRACK_MAXLEN 7928