diff --git a/NEWS b/NEWS
index 6c6651e78..eea6d32b4 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,9 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 - The 'enum' command can now create more than one type per invocation.
 
+- The POSIX compatibility mode has been amended to disable the special handling
+  of a repeated $IFS whitespace character as non-whitespace.
+
 2022-02-23:
 
 - When reading input from the keyboard, ksh now turns off nonblocking I/O
diff --git a/src/cmd/ksh93/include/defs.h b/src/cmd/ksh93/include/defs.h
index 6e3395c76..5158be0ab 100644
--- a/src/cmd/ksh93/include/defs.h
+++ b/src/cmd/ksh93/include/defs.h
@@ -127,6 +127,7 @@ extern Sfdouble_t	sh_arith(const char*);
 extern void		*sh_arithcomp(char*);
 extern pid_t 		sh_fork(int,int*);
 extern pid_t		_sh_fork(pid_t, int ,int*);
+extern void		sh_invalidate_ifs(void);
 extern char 		*sh_mactrim(char*,int);
 extern int 		sh_macexpand(struct argnod*,struct argnod**,int);
 extern int		sh_macfun(const char*,int);
diff --git a/src/cmd/ksh93/sh.1 b/src/cmd/ksh93/sh.1
index b4742c1fa..469dbca1d 100644
--- a/src/cmd/ksh93/sh.1
+++ b/src/cmd/ksh93/sh.1
@@ -2033,7 +2033,7 @@ Each single occurrence of
 an
 .SM
 .B IFS
-character in the string to be split,
+character in the string to be split
 that is not in the \f2isspace\^\fP character class, and any
 adjacent characters in
 .SM
@@ -2043,13 +2043,16 @@ One or more
 characters in
 .SM
 .B IFS
-that belong to the \f2isspace\^\fP character class,
+that belong to the \f2isspace\^\fP character class
 delimit a field.
 In addition, if the same \f2isspace\^\fP character appears
 consecutively inside
-.BR IFS ,
+.B IFS
+and the
+.B posix
+shell option is not on,
 this character is treated as if it were not in the \f2isspace\^\fP
-class, so that if
+class - for exmaple, if
 .BR IFS
 consists of two
 .B tab
@@ -7685,6 +7688,12 @@ In addition, while on, the \fBposix\fR option
 disables exporting variable type attributes to the environment for other ksh
 processes to import;
 .IP \[bu]
+disables the special handling of repeated
+.I isspace
+class characters in the
+.B IFS
+variable;
+.IP \[bu]
 causes file descriptors > 2 to be left open when invoking another program;
 .IP \[bu]
 disables the \fB&>\fR redirection shorthand;
diff --git a/src/cmd/ksh93/sh/args.c b/src/cmd/ksh93/sh/args.c
index 8fcb5c515..5e8488553 100644
--- a/src/cmd/ksh93/sh/args.c
+++ b/src/cmd/ksh93/sh/args.c
@@ -245,6 +245,7 @@ int sh_argopts(int argc,register char *argv[])
 				off_option(&newflags,SH_BRACEEXPAND);
 #endif
 				on_option(&newflags,SH_LETOCTAL);
+				sh_invalidate_ifs();
 			}
 			on_option(&newflags,o);
 			off_option(&sh.offoptions,o);
@@ -262,6 +263,7 @@ int sh_argopts(int argc,register char *argv[])
 				on_option(&newflags,SH_BRACEEXPAND);
 #endif
 				off_option(&newflags,SH_LETOCTAL);
+				sh_invalidate_ifs();
 			}
 			if(o==SH_XTRACE)
 				trace = 0;
diff --git a/src/cmd/ksh93/sh/init.c b/src/cmd/ksh93/sh/init.c
index 840abe282..f029b6c7d 100644
--- a/src/cmd/ksh93/sh/init.c
+++ b/src/cmd/ksh93/sh/init.c
@@ -549,6 +549,18 @@ static void put_ifs(register Namval_t* np,const char *val,int flags,Namfun_t *fp
 	}
 }
 
+/* Invalidate IFS state table */
+void sh_invalidate_ifs(void)
+{
+	Namval_t *np = sh_scoped(IFSNOD);
+	if(np)
+	{
+		struct ifs *ip = (struct ifs*)np->nvfun;
+		if(ip)
+			ip->ifsnp = 0;
+	}
+}
+
 /*
  * This is the lookup function for IFS
  * It keeps the sh.ifstable up to date
@@ -574,7 +586,8 @@ static char* get_ifs(register Namval_t* np, Namfun_t *fp)
 					continue;
 				}
 				n = S_DELIM;
-				if(c== *cp)
+				/* Treat a repeated char as S_DELIM even if whitespace, unless --posix is on */
+				if(c==*cp && !sh_isoption(SH_POSIX))
 					cp++;
 				else if(c=='\n')
 					n = S_NL;