diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
new file mode 100644
index ebb0994..c6a6ed3
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -88,17 +88,41 @@ DefineCollation(ParseState *pstate, List
 		if (strcmp(defel->defname, "from") == 0)
 			defelp = &fromEl;
 		else if (strcmp(defel->defname, "locale") == 0)
+		{
+			if (localeEl)
+				errorConflictingDefElem(defel, pstate);
 			defelp = &localeEl;
+		}
 		else if (strcmp(defel->defname, "lc_collate") == 0)
+		{
+			if (lccollateEl)
+				errorConflictingDefElem(defel, pstate);
 			defelp = &lccollateEl;
+		}
 		else if (strcmp(defel->defname, "lc_ctype") == 0)
+		{
+			if (lcctypeEl)
+				errorConflictingDefElem(defel, pstate);
 			defelp = &lcctypeEl;
+		}
 		else if (strcmp(defel->defname, "provider") == 0)
+		{
+			if (providerEl)
+				errorConflictingDefElem(defel, pstate);
 			defelp = &providerEl;
+		}
 		else if (strcmp(defel->defname, "deterministic") == 0)
+		{
+			if (deterministicEl)
+				errorConflictingDefElem(defel, pstate);
 			defelp = &deterministicEl;
+		}
 		else if (strcmp(defel->defname, "version") == 0)
+		{
+			if (versionEl)
+				errorConflictingDefElem(defel, pstate);
 			defelp = &versionEl;
+		}
 		else
 		{
 			ereport(ERROR,
@@ -112,11 +136,17 @@ DefineCollation(ParseState *pstate, List
 		*defelp = defel;
 	}
 
-	if ((localeEl && (lccollateEl || lcctypeEl))
-		|| (fromEl && list_length(parameters) != 1))
+	if (localeEl && (lccollateEl || lcctypeEl))
 		ereport(ERROR,
-				(errcode(ERRCODE_SYNTAX_ERROR),
-				 errmsg("conflicting or redundant options")));
+				errcode(ERRCODE_SYNTAX_ERROR),
+				errmsg("conflicting or redundant options"),
+				errdetail("LOCALE cannot be specified together with LC_COLLATE or LC_CTYPE."));
+
+	if (fromEl && list_length(parameters) != 1)
+		ereport(ERROR,
+				errcode(ERRCODE_SYNTAX_ERROR),
+				errmsg("conflicting or redundant options"),
+				errdetail("FROM cannot be specified together with any other options."));
 
 	if (fromEl)
 	{
diff --git a/src/test/regress/expected/collate.out b/src/test/regress/expected/collate.out
new file mode 100644
index 0b60b55..2468325
--- a/src/test/regress/expected/collate.out
+++ b/src/test/regress/expected/collate.out
@@ -701,6 +701,53 @@ View definition:
  SELECT ss.c1 + 1 AS c1p
    FROM ( SELECT 4 AS c1) ss;
 
+-- Check conflicting or redundant options in CREATE COLLATION
+-- LC_COLLATE
+CREATE COLLATION coll_dup_chk (LC_COLLATE = "POSIX", LC_COLLATE = "NONSENSE", LC_CTYPE = "POSIX");
+ERROR:  conflicting or redundant options
+LINE 1: ...ATE COLLATION coll_dup_chk (LC_COLLATE = "POSIX", LC_COLLATE...
+                                                             ^
+-- LC_CTYPE
+CREATE COLLATION coll_dup_chk (LC_CTYPE = "POSIX", LC_CTYPE = "NONSENSE", LC_COLLATE = "POSIX");
+ERROR:  conflicting or redundant options
+LINE 1: ...REATE COLLATION coll_dup_chk (LC_CTYPE = "POSIX", LC_CTYPE =...
+                                                             ^
+-- PROVIDER
+CREATE COLLATION coll_dup_chk (PROVIDER = icu, PROVIDER = NONSENSE, LC_COLLATE = "POSIX", LC_CTYPE = "POSIX");
+ERROR:  conflicting or redundant options
+LINE 1: CREATE COLLATION coll_dup_chk (PROVIDER = icu, PROVIDER = NO...
+                                                       ^
+-- LOCALE
+CREATE COLLATION case_sensitive (LOCALE = '', LOCALE = "NONSENSE");
+ERROR:  conflicting or redundant options
+LINE 1: CREATE COLLATION case_sensitive (LOCALE = '', LOCALE = "NONS...
+                                                      ^
+-- DETERMINISTIC
+CREATE COLLATION coll_dup_chk (DETERMINISTIC = TRUE, DETERMINISTIC = NONSENSE, LOCALE = '');
+ERROR:  conflicting or redundant options
+LINE 1: ...ATE COLLATION coll_dup_chk (DETERMINISTIC = TRUE, DETERMINIS...
+                                                             ^
+-- VERSION
+CREATE COLLATION coll_dup_chk (VERSION = '1', VERSION = "NONSENSE", LOCALE = '');
+ERROR:  conflicting or redundant options
+LINE 1: CREATE COLLATION coll_dup_chk (VERSION = '1', VERSION = "NON...
+                                                      ^
+-- LOCALE conflicts with LC_COLLATE and LC_CTYPE
+CREATE COLLATION coll_dup_chk (LC_COLLATE = "POSIX", LC_CTYPE = "POSIX", LOCALE = '');
+ERROR:  conflicting or redundant options
+DETAIL:  LOCALE cannot be specified together with LC_COLLATE or LC_CTYPE.
+-- LOCALE conflicts with LC_COLLATE
+CREATE COLLATION coll_dup_chk (LC_COLLATE = "POSIX", LOCALE = '');
+ERROR:  conflicting or redundant options
+DETAIL:  LOCALE cannot be specified together with LC_COLLATE or LC_CTYPE.
+-- LOCALE conflicts with LC_CTYPE
+CREATE COLLATION coll_dup_chk (LC_CTYPE = "POSIX", LOCALE = '');
+ERROR:  conflicting or redundant options
+DETAIL:  LOCALE cannot be specified together with LC_COLLATE or LC_CTYPE.
+-- FROM conflicts with any other option
+CREATE COLLATION coll_dup_chk (FROM = "C", VERSION = "1");
+ERROR:  conflicting or redundant options
+DETAIL:  FROM cannot be specified together with any other options.
 --
 -- Clean up.  Many of these table names will be re-used if the user is
 -- trying to run any platform-specific collation tests later, so we
diff --git a/src/test/regress/sql/collate.sql b/src/test/regress/sql/collate.sql
new file mode 100644
index 30f811b..c3d40fc
--- a/src/test/regress/sql/collate.sql
+++ b/src/test/regress/sql/collate.sql
@@ -272,6 +272,27 @@ SELECT c1+1 AS c1p FROM
   (SELECT ('4' COLLATE "C")::INT AS c1) ss;
 \d+ collate_on_int
 
+-- Check conflicting or redundant options in CREATE COLLATION
+-- LC_COLLATE
+CREATE COLLATION coll_dup_chk (LC_COLLATE = "POSIX", LC_COLLATE = "NONSENSE", LC_CTYPE = "POSIX");
+-- LC_CTYPE
+CREATE COLLATION coll_dup_chk (LC_CTYPE = "POSIX", LC_CTYPE = "NONSENSE", LC_COLLATE = "POSIX");
+-- PROVIDER
+CREATE COLLATION coll_dup_chk (PROVIDER = icu, PROVIDER = NONSENSE, LC_COLLATE = "POSIX", LC_CTYPE = "POSIX");
+-- LOCALE
+CREATE COLLATION case_sensitive (LOCALE = '', LOCALE = "NONSENSE");
+-- DETERMINISTIC
+CREATE COLLATION coll_dup_chk (DETERMINISTIC = TRUE, DETERMINISTIC = NONSENSE, LOCALE = '');
+-- VERSION
+CREATE COLLATION coll_dup_chk (VERSION = '1', VERSION = "NONSENSE", LOCALE = '');
+-- LOCALE conflicts with LC_COLLATE and LC_CTYPE
+CREATE COLLATION coll_dup_chk (LC_COLLATE = "POSIX", LC_CTYPE = "POSIX", LOCALE = '');
+-- LOCALE conflicts with LC_COLLATE
+CREATE COLLATION coll_dup_chk (LC_COLLATE = "POSIX", LOCALE = '');
+-- LOCALE conflicts with LC_CTYPE
+CREATE COLLATION coll_dup_chk (LC_CTYPE = "POSIX", LOCALE = '');
+-- FROM conflicts with any other option
+CREATE COLLATION coll_dup_chk (FROM = "C", VERSION = "1");
 
 --
 -- Clean up.  Many of these table names will be re-used if the user is