diff --git a/locale/programs/ld-monetary.c b/locale/programs/ld-monetary.c
index 3b0412b405..18698bbe94 100644
--- a/locale/programs/ld-monetary.c
+++ b/locale/programs/ld-monetary.c
@@ -196,21 +196,105 @@ No definition for %s category found"), "LC_MONETARY");
 	}
     }
 
+  /* Generally speaking there are 3 standards the define the default,
+     warning, and error behaviour of LC_MONETARY.  They are ISO/IEC TR 30112,
+     ISO/IEC 9899:2018 (ISO C17), and POSIX.1-2017.  Within 30112 we have the
+     definition of a standard i18n FDCC-set, which for LC_MONETARY has the
+     following default values:
+	int_curr_symbol		""
+	currency_symbol		""
+	mon_decimal_point	"<U002C>" i.e. ","
+	mon_thousand_sep	""
+	mon_grouping		"\177" i.e. CHAR_MAX
+	positive_sign		""
+	negative_sign		"<U002E>" i.e. "."
+	int_frac_digits		-1
+	frac_digits		-1
+	p_cs_precedes		-1
+	p_sep_by_space		-1
+	n_cs_precedes		-1
+	n_sep_by_space		-1
+	p_sign_posn		-1
+	n_sign_posn		-1
+    Under 30112 a keyword that is not provided implies an empty string ""
+    for string values or a -1 for integer values, and indicates the value
+    is unspecified with no default implied.  No errors are considered.
+    The exception is mon_grouping which is a string with a terminating
+    CHAR_MAX.
+    For POSIX Issue 7 we have:
+    https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap07.html
+    and again values not provided default to "" or -1, and indicate the value
+    is not available to the locale.  The exception is mon_grouping which is
+    a string with a terminating CHAR_MAX.  For the POSIX locale the values of
+    LC_MONETARY should be:
+	int_curr_symbol		""
+	currency_symbol		""
+	mon_decimal_point	""
+	mon_thousands_sep	""
+	mon_grouping		"\177" i.e. CHAR_MAX 
+	positive_sign		""
+	negative_sign		""
+	int_frac_digits		-1
+	frac_digits		-1
+	p_cs_precedes		-1
+	p_sep_by_space		-1
+	n_cs_precedes		-1
+	n_sep_by_space		-1
+	p_sign_posn		-1
+	n_sign_posn		-1
+	int_p_cs_precedes	-1
+	int_p_sep_by_space	-1
+	int_n_cs_precedes	-1
+	int_n_sep_by_space	-1
+	int_p_sign_posn		-1
+	int_n_sign_posn		-1
+    Like with 30112, POSIX also considers no error if the keywords are
+    missing, only that if the cateory as a whole is missing the referencing
+    of the category results in unspecified behaviour.
+    For ISO C17 there is no default value provided, but the localeconv
+    specification in 7.11.2.1 admits that members of char * type may point
+    to "" to indicate a value is not available or is of length zero.
+    The exception is decimal_point (not mon_decimal_point) which must be a
+    defined non-empty string.  The values of char, which are generally
+    mapped to integer values in 30112 and POSIX, must be non-negative
+    numbers that map to CHAR_MAX when a value is not available in the
+    locale.
+    In ISO C17 for the "C" locale all values are empty strings "", or
+    CHAR_MAX, with the exception of decimal_point which is "." (defined
+    in LC_NUMERIC).  ISO C17 makes no exception for mon_grouping like
+    30112 and POSIX, but a value of "" is functionally equivalent to
+    "\177" since neither defines a grouping (though the latter terminates
+    the grouping).
+
+    Lastly, we must consider the legacy C/POSIX locale that implemented
+    as a builtin in glibc and wether a default value mapping to the
+    C/POSIX locale may benefit the user from a compatibility perspective.
+
+    Thus given 30112, POSIX, ISO C, and the builtin C/POSIX locale we
+    need to pick appropriate defaults below.   */
+
+  /* The members of LC_MONETARY are handled in the order of their definition
+     in locale/categories.def.  Please keep them in that order.  */
+
+  /* The purpose of TEST_ELEM is to define a default value for the fields
+     in the category if the field was not defined in the cateory.  If the
+     category was present but we didn't see a definition for the field then
+     we also issue a warning, otherwise the only warning you get is the one
+     earlier when a default category is created (completely missing category).
+     This missing field warning is glibc-specific since no standard requires
+     this warning, but we consider it valuable to print a warning for all
+     missing fields in the category.  */
 #define TEST_ELEM(cat, initval) \
   if (monetary->cat == NULL)						      \
     {									      \
       if (! nothing)							      \
-	record_error (0, 0, _("%s: field `%s' not defined"),		      \
-		      "LC_MONETARY", #cat);				      \
+	record_warning (_("%s: field `%s' not defined"),		      \
+			"LC_MONETARY", #cat);				      \
       monetary->cat = initval;						      \
     }
 
+  /* Keyword: int_curr_symbol.  */
   TEST_ELEM (int_curr_symbol, "");
-  TEST_ELEM (currency_symbol, "");
-  TEST_ELEM (mon_thousands_sep, "");
-  TEST_ELEM (positive_sign, "");
-  TEST_ELEM (negative_sign, "");
-
   /* The international currency symbol must come from ISO 4217.  */
   if (monetary->int_curr_symbol != NULL)
     {
@@ -247,41 +331,63 @@ not correspond to a valid name in ISO 4217 [--no-warnings=intcurrsym]"),
 	}
     }
 
-  /* The decimal point must not be empty.  This is not said explicitly
-     in POSIX but ANSI C (ISO/IEC 9899) says in 4.4.2.1 it has to be
-     != "".  */
+  /* Keyword: currency_symbol */
+  TEST_ELEM (currency_symbol, "");
+
+  /* Keyword: mon_decimal_point */
+  /* ISO C17 7.11.2.1.3 explicitly allows mon_decimal_point to be the
+     empty string e.g. "".  This indicates the value is not available in the
+     current locale or is of zero length.  However, if the value was never
+     defined then we issue a warning and use a glibc-specific default.  ISO
+     30112 in the i18n FDCC-Set uses <U002C> ",", and POSIX Issue 7 in the
+     POSIX locale uses "".  It is specific to glibc that the default is <U002E>
+     "."; we retain this existing behaviour for backwards compatibility.  */
   if (monetary->mon_decimal_point == NULL)
     {
       if (! nothing)
-	record_error (0, 0, _("%s: field `%s' not defined"),
-		      "LC_MONETARY", "mon_decimal_point");
+	record_warning (_("%s: field `%s' not defined, using defaults"),
+			"LC_MONETARY", "mon_decimal_point");
       monetary->mon_decimal_point = ".";
       monetary->mon_decimal_point_wc = L'.';
     }
-  else if (monetary->mon_decimal_point[0] == '\0' && ! be_quiet && ! nothing)
+
+  /* Keyword: mon_thousands_sep */
+  if (monetary->mon_thousands_sep == NULL)
     {
-      record_error (0, 0, _("\
-%s: value for field `%s' must not be an empty string"),
-		    "LC_MONETARY", "mon_decimal_point");
+      if (! nothing)
+	record_warning (_("%s: field `%s' not defined, using defaults"),
+			"LC_MONETARY", "mon_thousands_sep");
+      monetary->mon_thousands_sep = "";
+      monetary->mon_thousands_sep_wc = L'\0';
     }
 
+  /* Keyword: mon_grouping */
   if (monetary->mon_grouping_len == 0)
     {
       if (! nothing)
-	record_error (0, 0, _("%s: field `%s' not defined"),
-		      "LC_MONETARY", "mon_grouping");
-
+	record_warning (_("%s: field `%s' not defined"),
+			"LC_MONETARY", "mon_grouping");
+      /* Missing entries are given 1 element in their bytearray with
+	 a value of CHAR_MAX which indicates that "No further grouping
+	 is to be performed" (functionally equivalent to ISO C's "C"
+	 locale default of ""). */
       monetary->mon_grouping = (char *) "\177";
       monetary->mon_grouping_len = 1;
     }
 
+  /* Keyword: positive_sign */
+  TEST_ELEM (positive_sign, "");
+
+  /* Keyword: negative_sign */
+  TEST_ELEM (negative_sign, "");
+
 #undef TEST_ELEM
 #define TEST_ELEM(cat, min, max, initval) \
   if (monetary->cat == -2)						      \
     {									      \
        if (! nothing)							      \
-	 record_error (0, 0, _("%s: field `%s' not defined"),		      \
-		       "LC_MONETARY", #cat);				      \
+	 record_warning (_("%s: field `%s' not defined"),		      \
+			 "LC_MONETARY", #cat);				      \
        monetary->cat = initval;						      \
     }									      \
   else if ((monetary->cat < min || monetary->cat > max)			      \
@@ -300,16 +406,11 @@ not correspond to a valid name in ISO 4217 [--no-warnings=intcurrsym]"),
   TEST_ELEM (p_sign_posn, -1, 4, -1);
   TEST_ELEM (n_sign_posn, -1, 4, -1);
 
-  /* The non-POSIX.2 extensions are optional.  */
-  if (monetary->duo_int_curr_symbol == NULL)
-    monetary->duo_int_curr_symbol = monetary->int_curr_symbol;
-  if (monetary->duo_currency_symbol == NULL)
-    monetary->duo_currency_symbol = monetary->currency_symbol;
-
-  if (monetary->duo_int_frac_digits == -2)
-    monetary->duo_int_frac_digits = monetary->int_frac_digits;
-  if (monetary->duo_frac_digits == -2)
-    monetary->duo_frac_digits = monetary->frac_digits;
+  /* Keyword: crncystr */
+  monetary->crncystr = (char *) xmalloc (strlen (monetary->currency_symbol)
+					 + 2);
+  monetary->crncystr[0] = monetary->p_cs_precedes ? '-' : '+';
+  strcpy (&monetary->crncystr[1], monetary->currency_symbol);
 
 #undef TEST_ELEM
 #define TEST_ELEM(cat, alt, min, max) \
@@ -327,6 +428,17 @@ not correspond to a valid name in ISO 4217 [--no-warnings=intcurrsym]"),
   TEST_ELEM (int_p_sign_posn, p_sign_posn, -1, 4);
   TEST_ELEM (int_n_sign_posn, n_sign_posn, -1, 4);
 
+  /* The non-POSIX.2 extensions are optional.  */
+  if (monetary->duo_int_curr_symbol == NULL)
+    monetary->duo_int_curr_symbol = monetary->int_curr_symbol;
+  if (monetary->duo_currency_symbol == NULL)
+    monetary->duo_currency_symbol = monetary->currency_symbol;
+
+  if (monetary->duo_int_frac_digits == -2)
+    monetary->duo_int_frac_digits = monetary->int_frac_digits;
+  if (monetary->duo_frac_digits == -2)
+    monetary->duo_frac_digits = monetary->frac_digits;
+
   TEST_ELEM (duo_p_cs_precedes, p_cs_precedes, -1, 1);
   TEST_ELEM (duo_p_sep_by_space, p_sep_by_space, -1, 2);
   TEST_ELEM (duo_n_cs_precedes, n_cs_precedes, -1, 1);
@@ -349,17 +461,15 @@ not correspond to a valid name in ISO 4217 [--no-warnings=intcurrsym]"),
   if (monetary->duo_valid_to == 0)
     monetary->duo_valid_to = 99991231;
 
+  /* Keyword: conversion_rate */
   if (monetary->conversion_rate[0] == 0)
     {
       monetary->conversion_rate[0] = 1;
       monetary->conversion_rate[1] = 1;
     }
 
-  /* Create the crncystr entry.  */
-  monetary->crncystr = (char *) xmalloc (strlen (monetary->currency_symbol)
-					 + 2);
-  monetary->crncystr[0] = monetary->p_cs_precedes ? '-' : '+';
-  strcpy (&monetary->crncystr[1], monetary->currency_symbol);
+  /* A value for monetary-decimal-point-wc was set when
+     monetary_decimal_point was set, likewise for monetary-thousands-sep-wc.  */
 }
 
 
