diff --git a/src/co65/error.h b/src/co65/error.h
index 9eab1e7ba..48ba30caf 100644
--- a/src/co65/error.h
+++ b/src/co65/error.h
@@ -52,10 +52,10 @@
 void Warning (const char* Format, ...) attribute((format(printf,1,2)));
 /* Print a warning message */
 
-void Error (const char* Format, ...) attribute((format(printf,1,2)));
+void Error (const char* Format, ...) attribute((noreturn, format(printf,1,2)));
 /* Print an error message and die */
 
-void Internal (const char* Format, ...) attribute((format(printf,1,2)));
+void Internal (const char* Format, ...) attribute((noreturn, format(printf,1,2)));
 /* Print an internal error message and die */
 
 
diff --git a/src/co65/o65.c b/src/co65/o65.c
index 976e23a70..5a14d17f9 100644
--- a/src/co65/o65.c
+++ b/src/co65/o65.c
@@ -187,7 +187,8 @@ static O65Import* ReadO65Import (FILE* F)
     do {
         C = Read8 (F);
         if (Len >= sizeof (Buf)) {
-            Error ("Imported identifier exceeds maximum size (%u)", sizeof (Buf));
+            Error ("Imported identifier exceeds maximum size (%u)",
+                   (unsigned) sizeof (Buf));
         }
         Buf[Len++] = C;
     } while (C != '\0');
@@ -281,7 +282,8 @@ static O65Export* ReadO65Export (FILE* F, const O65Header* H)
     do {
         C = Read8 (F);
         if (Len >= sizeof (Buf)) {
-            Error ("Exported identifier exceeds maximum size (%u)", sizeof (Buf));
+            Error ("Exported identifier exceeds maximum size (%u)",
+                   (unsigned) sizeof (Buf));
         }
         Buf[Len++] = C;
     } while (C != '\0');
diff --git a/src/od65/error.h b/src/od65/error.h
index f4dbf3fd4..af5c907fd 100644
--- a/src/od65/error.h
+++ b/src/od65/error.h
@@ -6,10 +6,10 @@
 /*                                                                           */
 /*                                                                           */
 /*                                                                           */
-/* (C) 1998-2000 Ullrich von Bassewitz                                       */
-/*               Wacholderweg 14                                             */
-/*               D-70597 Stuttgart                                           */
-/* EMail:        uz@musoftware.de                                            */
+/* (C) 1998-2003 Ullrich von Bassewitz                                       */
+/*               Römerstrasse 52                                             */
+/*               D-70794 Filderstadt                                         */
+/* EMail:        uz@cc65.org                                                 */
 /*                                                                           */
 /*                                                                           */
 /* This software is provided 'as-is', without any expressed or implied       */
@@ -52,10 +52,10 @@
 void Warning (const char* Format, ...) attribute((format(printf,1,2)));
 /* Print a warning message */
 
-void Error (const char* Format, ...) attribute((format(printf,1,2)));
+void Error (const char* Format, ...) attribute((noreturn, format(printf,1,2)));
 /* Print an error message and die */
 
-void Internal (const char* Format, ...) attribute((format(printf,1,2)));
+void Internal (const char* Format, ...) attribute((noreturn, format(printf,1,2)));
 /* Print an internal error message and die */