diff --git a/contrib/file_fdw/expected/file_fdw.out b/contrib/file_fdw/expected/file_fdw.out
index df8d43b3749..246e3d3e566 100644
--- a/contrib/file_fdw/expected/file_fdw.out
+++ b/contrib/file_fdw/expected/file_fdw.out
@@ -48,6 +48,10 @@ SET ROLE regress_file_fdw_superuser;
 CREATE USER MAPPING FOR regress_file_fdw_superuser SERVER file_server;
 CREATE USER MAPPING FOR regress_no_priv_user SERVER file_server;
 -- validator tests
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (foo 'bar');  -- ERROR
+ERROR:  invalid option "foo"
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS ("a=b" 'true');  -- ERROR
+ERROR:  invalid option name "a=b": must not contain "="
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'xml');  -- ERROR
 ERROR:  COPY format "xml" not recognized
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', quote ':');          -- ERROR
diff --git a/contrib/file_fdw/sql/file_fdw.sql b/contrib/file_fdw/sql/file_fdw.sql
index 2cdbe7a8a4c..1a397ad4bd1 100644
--- a/contrib/file_fdw/sql/file_fdw.sql
+++ b/contrib/file_fdw/sql/file_fdw.sql
@@ -55,6 +55,8 @@ CREATE USER MAPPING FOR regress_file_fdw_superuser SERVER file_server;
 CREATE USER MAPPING FOR regress_no_priv_user SERVER file_server;
 
 -- validator tests
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (foo 'bar');  -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS ("a=b" 'true');  -- ERROR
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'xml');  -- ERROR
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', quote ':');          -- ERROR
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', escape ':');         -- ERROR
diff --git a/src/backend/access/common/reloptions.c b/src/backend/access/common/reloptions.c
index 46c1dce222d..50747c16396 100644
--- a/src/backend/access/common/reloptions.c
+++ b/src/backend/access/common/reloptions.c
@@ -1243,8 +1243,9 @@ transformRelOptions(Datum oldOptions, List *defList, const char *namspace,
 		}
 		else
 		{
-			text	   *t;
+			const char *name;
 			const char *value;
+			text	   *t;
 			Size		len;
 
 			/*
@@ -1291,11 +1292,19 @@ transformRelOptions(Datum oldOptions, List *defList, const char *namspace,
 			 * have just "name", assume "name=true" is meant.  Note: the
 			 * namespace is not output.
 			 */
+			name = def->defname;
 			if (def->arg != NULL)
 				value = defGetString(def);
 			else
 				value = "true";
 
+			/* Insist that name not contain "=", else "a=b=c" is ambiguous */
+			if (strchr(name, '=') != NULL)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("invalid option name \"%s\": must not contain \"=\"",
+								name)));
+
 			/*
 			 * This is not a great place for this test, but there's no other
 			 * convenient place to filter the option out. As WITH (oids =
@@ -1303,7 +1312,7 @@ transformRelOptions(Datum oldOptions, List *defList, const char *namspace,
 			 * amount of ugly.
 			 */
 			if (acceptOidsOff && def->defnamespace == NULL &&
-				strcmp(def->defname, "oids") == 0)
+				strcmp(name, "oids") == 0)
 			{
 				if (defGetBoolean(def))
 					ereport(ERROR,
@@ -1313,11 +1322,11 @@ transformRelOptions(Datum oldOptions, List *defList, const char *namspace,
 				continue;
 			}
 
-			len = VARHDRSZ + strlen(def->defname) + 1 + strlen(value);
+			len = VARHDRSZ + strlen(name) + 1 + strlen(value);
 			/* +1 leaves room for sprintf's trailing null */
 			t = (text *) palloc(len + 1);
 			SET_VARSIZE(t, len);
-			sprintf(VARDATA(t), "%s=%s", def->defname, value);
+			sprintf(VARDATA(t), "%s=%s", name, value);
 
 			astate = accumArrayResult(astate, PointerGetDatum(t),
 									  false, TEXTOID,
diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index c14e038d54f..8d2d7431544 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -71,15 +71,26 @@ optionListToArray(List *options)
 	foreach(cell, options)
 	{
 		DefElem    *def = lfirst(cell);
+		const char *name;
 		const char *value;
 		Size		len;
 		text	   *t;
 
+		name = def->defname;
 		value = defGetString(def);
-		len = VARHDRSZ + strlen(def->defname) + 1 + strlen(value);
+
+		/* Insist that name not contain "=", else "a=b=c" is ambiguous */
+		if (strchr(name, '=') != NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("invalid option name \"%s\": must not contain \"=\"",
+							name)));
+
+		len = VARHDRSZ + strlen(name) + 1 + strlen(value);
+		/* +1 leaves room for sprintf's trailing null */
 		t = palloc(len + 1);
 		SET_VARSIZE(t, len);
-		sprintf(VARDATA(t), "%s=%s", def->defname, value);
+		sprintf(VARDATA(t), "%s=%s", name, value);
 
 		astate = accumArrayResult(astate, PointerGetDatum(t),
 								  false, TEXTOID,