diff --git a/mps/src/assert.c b/mps/src/assert.c
index 7c38915bcd4..738a9b51c05 100644
--- a/mps/src/assert.c
+++ b/mps/src/assert.c
@@ -1,16 +1,16 @@
 /* impl.c.assert: ASSERTION IMPLEMENTATION
  *
- * $HopeName: MMsrc!assert.c(trunk.7) $
+ * $HopeName: MMsrc!assert.c(trunk.8) $
  *
  * This source provides the AssertFail function which is
  * invoked by the assertion macros (see impl.h.assert).
  * It also provides for user-installed assertion failure handlers.
  *
- * Notes
  *
- * 3. To be really solid, assert should write the information into a
- * buffer before reaching the handler, so that it can be recovered
- * even if printing fails.  richard 1994-11-15
+ * NOTES
+ *
+ * .note.assert-buffer: The Assertion Buffer is not used.  In the future
+ * we probably ought to use it. (see .buffer.* below)
  */
 
 #include "mpm.h"
@@ -24,6 +24,20 @@
 
 Word CheckLevel = CheckSHALLOW;
 
+
+/* Assertion buffer
+ *
+ * .buffer.purpose: the assertion buffer serves two purposes:
+ * .buffer.purpose.modify: assertion strings are picked apart and
+ * modified before being passed to assertion handlers, this
+ * buffer is used to do that.
+ * .buffer.purpose.store: Debuggers, post-mortem dumps, etc, can retrieve the
+ * assertion text even if for some reason printing the text out failed.
+ * [note this is not used, see .note.buffer]
+ */
+
+char AssertBuffer[ASSERT_BUFFER_SIZE];
+
 static void AssertLib(const char *cond, const char *id,
                       const char *file, unsigned line)
 {
@@ -63,9 +77,8 @@ AssertHandler AssertInstall(AssertHandler new)
  * handler returns the progam continues.
  */
 
-void AssertFail(const char *cond, const char *id,
-                const char *file, unsigned line)
+void AssertFail1(const char *s)
 {
   if(handler != NULL)
-    (*handler)(cond, id, file, line);
+    (*handler)(s, "", "", 0);
 }
diff --git a/mps/src/check.h b/mps/src/check.h
index 12515d6a669..288326b0435 100644
--- a/mps/src/check.h
+++ b/mps/src/check.h
@@ -1,6 +1,6 @@
 /* impl.h.check: ASSERTION INTERFACE
  *
- * $HopeName: MMsrc!check.h(trunk.8) $
+ * $HopeName: MMsrc!check.h(trunk.9) $
  *
  * This header defines a family of AVER and NOTREACHED macros. The
  * macros should be used to instrument and annotate code with
@@ -38,17 +38,20 @@
 
 #elif defined(MPS_HOT_RED) 
 
-#define AVER(cond)                  ASSERT(cond)
-#define AVERT(type, val)            ASSERT(type ## Check(val))
+#define AVER(cond)                  ASSERT(cond, #cond)
+#define AVERT(type, val)            ASSERT(type ## Check(val), \
+        "TypeCheck " #type ": " #val)
 #define AVER_CRITICAL(cond)         NOCHECK(cond)
 #define AVERT_CRITICAL(type, val)   NOCHECK(type ## Check(val))
 
 #elif defined(MPS_COOL)
 
-#define AVER(cond)                  ASSERT(cond)
-#define AVERT(type, val)            ASSERT(type ## Check(val))
-#define AVER_CRITICAL(cond)         ASSERT(cond)
-#define AVERT_CRITICAL(type, val)   ASSERT(type ## Check(val))
+#define AVER(cond)                  ASSERT(cond, #cond)
+#define AVERT(type, val)            ASSERT(type ## Check(val), \
+        "TypeCheck " #type ": " #val)
+#define AVER_CRITICAL(cond)         ASSERT(cond, #cond)
+#define AVERT_CRITICAL(type, val)   ASSERT(type ## Check(val), \
+        "TypeCheck " #type ": " #val)
 
 #else
 
@@ -61,14 +64,20 @@ typedef void (*AssertHandler)(const char *cond, const char *id,
 extern AssertHandler AssertInstall(AssertHandler handler);
 extern AssertHandler AssertDefault(void);
 
-extern void AssertFail(const char *cond, const char *id,
-                       const char *file, unsigned line);
+extern void AssertFail1(const char *s);
 
-#define ASSERT(cond) \
+/* STR(x) expands into a string of the expansion of x. */
+/* Eg, if we have: */
+/* #define a b */
+/* STR(a) will expand into "b". */
+/* @@@@ really STR belongs in some generic support file. */
+#define STR_(x) #x
+#define STR(x) STR_(x)
+
+#define ASSERT(cond, condstring) \
   BEGIN \
     if(cond) NOOP; else \
-      AssertFail(#cond, FileSrcIdStruct.hopename, \
-                 FileSrcIdStruct.file, __LINE__); \
+      AssertFail1(condstring "\n" __FILE__ "\n" STR(__LINE__)); \
   END
 
 		 
@@ -80,16 +89,13 @@ extern void AssertFail(const char *cond, const char *id,
     
 #define NOTREACHED \
   BEGIN \
-    AssertFail("unreachable statement", \
-               FileSrcIdStruct.hopename, FileSrcIdStruct.file, \
-               __LINE__); \
+    AssertFail1("unreachable statement" "\n" __FILE__ "\n" STR(__LINE__)); \
   END
 
-#define CHECKC(cond) \
+#define CHECKC(cond, condstring) \
   BEGIN \
     if(cond) NOOP; else \
-      AssertFail(#cond, FileSrcIdStruct.hopename, \
-                 FileSrcIdStruct.file, __LINE__); \
+      AssertFail1(condstring "\n" __FILE__ "\n" STR(__LINE__)); \
   END
 
 
@@ -122,7 +128,8 @@ extern void AssertFail(const char *cond, const char *id,
 #elif defined(MPS_HOT_RED)
 
 /* CHECKS -- Check Signature */
-#define CHECKS(type, val)       CHECKC(CHECKT(type, val))
+#define CHECKS(type, val)       CHECKC(CHECKT(type, val), \
+	"SigCheck " #type ": " #val)
 
 #define CHECKL(cond)       NOCHECK(cond)
 #define CHECKD(type, val)  NOCHECK(CHECKT(type, val))
@@ -131,7 +138,8 @@ extern void AssertFail(const char *cond, const char *id,
 #elif defined(MPS_COOL)
 
 /* CHECKS -- Check Signature */
-#define CHECKS(type, val)       CHECKC(CHECKT(type, val))
+#define CHECKS(type, val)       CHECKC(CHECKT(type, val), \
+	"SigCheck " #type ": " #val)
 
 /* CHECKL -- Check Local Invariant */
 /* Could make this an expression using ?: */
@@ -143,7 +151,7 @@ extern void AssertFail(const char *cond, const char *id,
       break; \
     case CheckSHALLOW: \
     case CheckDEEP: \
-      CHECKC(cond); \
+      CHECKC(cond, #cond); \
       break; \
     default: \
       NOTREACHED; \
@@ -159,10 +167,12 @@ extern void AssertFail(const char *cond, const char *id,
       NOOP; \
       break; \
     case CheckSHALLOW: \
-      CHECKC(CHECKT(type, val)); \
+      CHECKC(CHECKT(type, val), \
+             "SigCheck " #type ": " #val); \
       break; \
     case CheckDEEP: \
-      CHECKC(type ## Check(val)); \
+      CHECKC(type ## Check(val), \
+             "TypeCheck " #type ": " #val); \
       break; \
     default: \
       NOTREACHED; \
@@ -179,7 +189,8 @@ extern void AssertFail(const char *cond, const char *id,
       break; \
     case CheckSHALLOW: \
     case CheckDEEP: \
-      CHECKC(CHECKT(type, val)); \
+      CHECKC(CHECKT(type, val), \
+             "SigCheck " #type ": " #val); \
       break; \
     default: \
       NOTREACHED; \
diff --git a/mps/src/config.h b/mps/src/config.h
index 5a202dc6ede..6cd22094009 100644
--- a/mps/src/config.h
+++ b/mps/src/config.h
@@ -1,7 +1,7 @@
 /* impl.h.config: MPS CONFIGURATION
  *
  * Copyright (C) 1997, 1998 Harlequin Group, all rights reserved.
- * $HopeName: MMsrc!config.h(trunk.20) $
+ * $HopeName: MMsrc!config.h(trunk.21) $
  *
  * .readership: MPS developers.
  */
@@ -210,6 +210,13 @@
 #define EVENT_HEADER_SIZE       ((Count)3)
 
 
+/* Assert Buffer
+ *
+ * The Assert Buffer lives in assert.c */
+
+#define ASSERT_BUFFER_SIZE      ((Size)512)
+
+
 /* memcpy configuration
  *
  * PoolClass AMC requires an efficient memcpy routine.