diff --git a/src/cmd/ksh93/include/defs.h b/src/cmd/ksh93/include/defs.h
index 55ca23b21..b1b006ade 100644
--- a/src/cmd/ksh93/include/defs.h
+++ b/src/cmd/ksh93/include/defs.h
@@ -30,8 +30,8 @@
 #endif
 
 #include	<ast.h>
-#if !defined(AST_VERSION) || AST_VERSION < 20220208
-#error libast version 20220208 or later is required
+#if !defined(AST_VERSION) || AST_VERSION < 20220801
+#error libast version 20220801 or later is required
 #endif
 #if !_lib_fork
 #error In 2021, ksh joined the 21st century and started requiring fork(2).
diff --git a/src/cmd/ksh93/sh/init.c b/src/cmd/ksh93/sh/init.c
index 85e6fac1e..8e7613335 100644
--- a/src/cmd/ksh93/sh/init.c
+++ b/src/cmd/ksh93/sh/init.c
@@ -222,12 +222,11 @@ static int		shlvl;
 static int		rand_shift;
 
 /*
- * out of memory routine for stak routines
+ * Exception callback routine for stk(3)/stak(3) and sh_*alloc wrappers.
  */
-static noreturn char *nomemory(int unused)
+static noreturn char *nomemory(size_t s)
 {
-	NOT_USED(unused);
-	errormsg(SH_DICT, ERROR_SYSTEM|ERROR_PANIC, "out of memory");
+	errormsg(SH_DICT, ERROR_SYSTEM|ERROR_PANIC, "out of memory (needed %llu bytes)", (uintmax_t)s);
 	UNREACHABLE();
 }
 
@@ -239,7 +238,7 @@ void *sh_malloc(size_t size)
 {
 	void *cp = malloc(size);
 	if(!cp)
-		nomemory(0);
+		nomemory(size);
 	return(cp);
 }
 
@@ -247,7 +246,7 @@ void *sh_realloc(void *ptr, size_t size)
 {
 	void *cp = realloc(ptr, size);
 	if(!cp)
-		nomemory(0);
+		nomemory(size);
 	return(cp);
 }
 
@@ -255,7 +254,7 @@ void *sh_calloc(size_t nmemb, size_t size)
 {
 	void *cp = calloc(nmemb, size);
 	if(!cp)
-		nomemory(0);
+		nomemory(size);
 	return(cp);
 }
 
@@ -263,7 +262,7 @@ char *sh_strdup(const char *s)
 {
 	char *dup = strdup(s);
 	if(!dup)
-		nomemory(0);
+		nomemory(strlen(s)+1);
 	return(dup);
 }
 
@@ -271,7 +270,7 @@ void *sh_memdup(const void *s, size_t n)
 {
 	void *dup = memdup(s, n);
 	if(!dup)
-		nomemory(0);
+		nomemory(n);
 	return(dup);
 }
 
@@ -279,7 +278,7 @@ char *sh_getcwd(void)
 {
 	char *cwd = getcwd(NIL(char*), 0);
 	if(!cwd && errno==ENOMEM)
-		nomemory(0);
+		nomemory(PATH_MAX);
 	return(cwd);
 }
 
diff --git a/src/lib/libast/features/api b/src/lib/libast/features/api
index 1daf15f43..58aeebf3e 100644
--- a/src/lib/libast/features/api
+++ b/src/lib/libast/features/api
@@ -1,6 +1,6 @@
 iff AST_API
 
-ver ast 20220208
+ver ast 20220801
 
 api ast 20120528 regexec regnexec regrexec regsubexec
 
diff --git a/src/lib/libast/include/stk.h b/src/lib/libast/include/stk.h
index fb110e35c..ceccd431f 100644
--- a/src/lib/libast/include/stk.h
+++ b/src/lib/libast/include/stk.h
@@ -45,7 +45,7 @@
 extern Sfio_t		_Stk_data;
 
 extern Stk_t*		stkopen(int);
-extern Stk_t*		stkinstall(Stk_t*, char*(*)(int));
+extern Stk_t*		stkinstall(Stk_t*, char*(*)(size_t));
 extern int		stkclose(Stk_t*);
 extern unsigned int	stklink(Stk_t*);
 extern char*		stkalloc(Stk_t*, size_t);
diff --git a/src/lib/libast/man/stak.3 b/src/lib/libast/man/stak.3
index 2a354cefc..390c66e30 100644
--- a/src/lib/libast/man/stak.3
+++ b/src/lib/libast/man/stak.3
@@ -10,7 +10,7 @@
 #include <stak.h>
 
 Stak_t *stakcreate(int \fIflags\fP);
-Stak_t *stakinstall(Stak_t *\fIstack\fP, char *(\fIoverflow\fP)(int));
+Stak_t *stakinstall(Stak_t *\fIstack\fP, char *(\fIoverflow\fP)(size_t));
 int stakdelete(Stak_t *\fIstack\fP);
 unsigned int staklink(Stak_t *\fIstack\fP)
 
@@ -29,6 +29,11 @@ char *stakfreeze(unsigned \fIextra\fP);
 .fi
 .SH DESCRIPTION
 .PP
+(This interface is obsolete; it is now simply a set of macros
+that translate these calls into \f3stk\fP(3) and \f3sfio\fP(3) calls
+using \f3stkstd\fP.
+The following description should continue to apply to the old calls.)
+.PP
 \f3stak\fP is a package of routines designed to provide efficient
 stack oriented dynamic storage.
 A stack abstraction consists of an ordered list of contiguous
@@ -36,10 +41,12 @@ memory regions, called stack frames, that can hold objects of
 arbitrary size.
 A stack is represented by the type \f3Stak_t\fP
 defined in header \f3<stak.h>\fP.
+.PP
 At any instant there is one active stack.
 Variable size objects can be
 added to the active stack
 and programs can reference these objects directly with pointers.
+.PP
 In addition, the last object on the stack
 (referred to here as the current object)
 can be built incrementally.
@@ -53,6 +60,7 @@ relative offsets ranging from zero to the current offset of the object.
 There is a preset initial active stack.
 To use an additional stack, it is necessary to create it and to
 install it as the active stack.
+.PP
 A stack is created with the \f3stakcreate\fP() function.
 The \fIflags\fP argument is an options bitmask.
 If the \f3STAK_SMALL\fP bit is set, the stack allocates memory in
@@ -61,8 +69,10 @@ If successful,
 \f3stakcreate\fP() returns a pointer to a stack whose reference
 count is 1.
 Otherwise, \f3stakcreate\fP() returns a null pointer.
+.PP
 The \f3staklink\fP() function increases the reference count for the
 given \fIstack\fP and returns the increased count.
+.PP
 The \f3stakinstall\fP() function
 makes the specified \fIstack\fP the active stack and returns a pointer
 to the previous active stack.
@@ -82,6 +92,7 @@ When \fIstack\fP is a null pointer,
 the active stack is not changed
 but the \fIoverflow\fP function for the active stack can be changed
 and a pointer to the active stack is returned.
+.PP
 The \f3stakdelete\fP() function decrements the reference count and
 frees the memory associated with
 the specified stack
@@ -122,6 +133,7 @@ There is a current offset associated with the current object that
 determines where subsequent operations apply.
 Initially, this offset is zero, and the offset changes as a result
 of the operations you specify.
+.PP
 The \f3stakseek\fP() function is used set the offset for the
 current object.
 The \fIoffset\fP argument to \f3stakseek\fP() specifies the new
@@ -130,14 +142,17 @@ The frame will be extended or moved
 if \f3offset\fP causes the new current offset to extend beyond the
 current frame.
 \f3stakseek\fP() returns a pointer to the beginning of the current object.
+.PP
 The \f3staktell\fP() function gives the offset of the current object.
 .PP
 The \f3stakputc\fP() function adds a given character to the current object
 on the stack.
 The current offset is advanced by 1.
+.PP
 The \f3stakputs\fP() function appends the given \fIstring\fP onto the current
 object in the stack and returns the length of the string.
 The current offset is advanced by the length of the string.
+.PP
 The \f3stakwrite\fP() function appends the given \fIsize\fP byte memory
 region starting at \fIaddress\fP onto the current
 object in the stack and advances the current offset by \fIsize\fP.
@@ -148,13 +163,13 @@ for the current object into a memory address on the stack.
 This address is only valid until another stack operation is given.
 The result is not defined if \fIoffset\fP exceeds the size of the current
 object.
+.PP
 The \f3stakfreeze\fP()
 function terminates the current object on the
 stack and returns a pointer to the beginning of this object.
 If \fIextra\fP is non-zero, \fIextra\fP bytes are added to the stack
 before the current object is terminated.  The first added byte will
 contain zero and the contents of the remaining bytes are undefined.
-.PP
 .SH HISTORY
 The
 \f3stak\fP
diff --git a/src/lib/libast/man/stk.3 b/src/lib/libast/man/stk.3
index 3c61f648b..cfc2959ad 100644
--- a/src/lib/libast/man/stk.3
+++ b/src/lib/libast/man/stk.3
@@ -10,7 +10,7 @@
 #include <stk.h>
 
 Stk_t *stkopen(int \fIflags\fP);
-Stk_t *stkinstall(Stk_t *\fIstack\fP, char *(\fIoverflow\fP)(int));
+Stk_t *stkinstall(Stk_t *\fIstack\fP, char *(\fIoverflow\fP)(size_t));
 int stkclose(Stk_t *\fIstack\fP);
 unsigned int stklink(Stk_t *\fIstack\fP)
 
@@ -36,11 +36,13 @@ A stack is represented by the type \f3Stk_t\fP
 defined in header \f3<stk.h>\fP.
 The type \f3Stk_t\fP is compatible with the type \f3Sfio_t\fP
 defined by the \f3sfio\fP(3) library.
+.PP
 At any instant there is one active stack which can be referenced
 by the constant \f3stkstd\fP.
 Variable size objects can be
 added to the active stack
 and programs can reference these objects directly with pointers.
+.PP
 In addition, the last object on the stack
 (referred to here as the current object)
 can be built incrementally.
@@ -54,23 +56,26 @@ relative offsets ranging from zero to the current offset of the object.
 There is a preset initial active stack.
 To use an additional stack, it is necessary to create it and to
 install it as the active stack.
+.PP
 A stack is created with the \f3stkopen\fP() function.
 The \fIflags\fP argument is an options bitmask.
 If the \f3STK_SMALL\fP bit is set, the stack allocates memory in
 small blocks, optimizing for memory usage at the expense of performance.
 If the \f3STK_NULL\fP bit is set, a stack overflow will cause stack
-operations to return a null pointer instead of throwing an error.
+operations to return a null pointer instead of throwing an exception.
 If successful,
 \f3stkopen\fP() returns a pointer to a stack whose reference
 count is 1.
 Otherwise, \f3stkopen\fP() returns a null pointer.
+.PP
 The \f3stklink\fP() function increases the reference count for the
 given \fIstack\fP and returns the increased count.
+.PP
 The \f3stkinstall\fP() function
 makes the specified \fIstack\fP the active stack and returns a pointer
 to the previous active stack.
-When the \fIoverflow\fP argument is not null,
-it specifies a function that will
+If the \fIoverflow\fP argument is not null and the stack was not opened with
+the \f3STK_NULL\fP option, \fIoverflow\fP specifies a function that will
 be called whenever \f3malloc\fP(3) fails while trying to grow the
 stack.
 The \fIoverflow\fP function will be called with the size that was passed
@@ -85,6 +90,7 @@ When \fIstack\fP is a null pointer,
 the active stack is not changed
 but the \fIoverflow\fP function for the active stack can be changed
 and a pointer to the active stack is returned.
+.PP
 The \f3stkclose\fP() function decrements the reference count and
 frees the memory associated with
 the specified stack
@@ -126,6 +132,7 @@ There is a current offset associated with the current object that
 determines where subsequent operations apply.
 Initially, this offset is zero, and the offset changes as a result
 of the operations you specify.
+.PP
 The \f3stkseek\fP() function is used set the offset for the
 current object.
 The \fIoffset\fP argument to \f3stkseek\fP() specifies the new
@@ -134,6 +141,7 @@ The frame will be extended or moved
 if \f3offset\fP causes the new current offset to extend beyond the
 current frame.
 \f3stkseek\fP() returns a pointer to the beginning of the current object.
+.PP
 The \f3stktell\fP() function gives the offset of the current object.
 .PP
 The \f3stkptr\fP() function converts the given \f3offset\fP
@@ -141,6 +149,7 @@ for the current object into a memory address on the stack.
 This address is only valid until another stack operation is given.
 The result is not defined if \fIoffset\fP exceeds the size of the current
 object.
+.PP
 The \f3stkfreeze\fP()
 function terminates the current object on the
 stack and returns a pointer to the beginning of this object.
@@ -151,7 +160,6 @@ contain zero and the contents of the remaining bytes are undefined.
 The \f3stkon\fP()
 function returns non-zero if the address given by \fIaddr\fP is
 on the stack \fIstack\fP and \f30\fP otherwise.
-.PP
 .SH HISTORY
 The
 \f3stk\fP
diff --git a/src/lib/libast/misc/stk.c b/src/lib/libast/misc/stk.c
index d6d1c0da5..c5ebb5395 100644
--- a/src/lib/libast/misc/stk.c
+++ b/src/lib/libast/misc/stk.c
@@ -51,7 +51,7 @@
 #define STK_FSIZE	(1024*sizeof(char*))
 #define STK_HDRSIZE	(sizeof(Sfio_t)+sizeof(Sfdisc_t))
 
-typedef char* (*_stk_overflow_)(int);
+typedef char* (*_stk_overflow_)(size_t);
 
 static int stkexcept(Sfio_t*,int,void*,Sfdisc_t*);
 static Sfdisc_t stkdisc = { 0, 0, 0, stkexcept };
@@ -113,7 +113,7 @@ static const char Omsg[] = "malloc failed while growing stack\n";
 /*
  * default overflow exception
  */
-static noreturn char *overflow(int n)
+static noreturn char *overflow(size_t n)
 {
 	NoP(n);
 	write(2,Omsg, sizeof(Omsg)-1);