diff --git a/expected/jsquery.out b/expected/jsquery.out
index 6767433..8c8d3b1 100644
--- a/expected/jsquery.out
+++ b/expected/jsquery.out
@@ -3,6 +3,11 @@ set escape_string_warning=off;
 set standard_conforming_strings=on;
 CREATE TABLE test_jsquery (v jsonb);
 \copy test_jsquery from 'data/test_jsquery.data'
+select ''::jsquery;
+ERROR:  bad jsquery representation
+LINE 1: select ''::jsquery;
+               ^
+DETAIL:  No symbols read at the end of input
 select 'asd.zzz = 13'::jsquery;
      jsquery      
 ------------------
diff --git a/expected/jsquery_1.out b/expected/jsquery_1.out
index a265cc9..ea1f6dc 100644
--- a/expected/jsquery_1.out
+++ b/expected/jsquery_1.out
@@ -3,6 +3,11 @@ set escape_string_warning=off;
 set standard_conforming_strings=on;
 CREATE TABLE test_jsquery (v jsonb);
 \copy test_jsquery from 'data/test_jsquery.data'
+select ''::jsquery;
+ERROR:  bad jsquery representation
+LINE 1: select ''::jsquery;
+               ^
+DETAIL:  No symbols read at the end of input
 select 'asd.zzz = 13'::jsquery;
      jsquery      
 ------------------
diff --git a/jsquery_gram.y b/jsquery_gram.y
index b6a4978..fd05e7a 100644
--- a/jsquery_gram.y
+++ b/jsquery_gram.y
@@ -258,7 +258,9 @@ result:
 										*result = $1;
 										(void) yynerrs;		/* suppress compiler warning */
 									}
-	| /* EMPTY */					{ *result = NULL; }
+	| /* EMPTY */					{
+										*result = NULL;
+										yyerror(NULL, "No symbols read"); }
 	;
 
 array:
diff --git a/jsquery_io.c b/jsquery_io.c
index ec44d5c..8a4b9ac 100644
--- a/jsquery_io.c
+++ b/jsquery_io.c
@@ -162,17 +162,12 @@ jsquery_in(PG_FUNCTION_ARGS)
 
 	appendStringInfoSpaces(&buf, VARHDRSZ);
 
-	if (jsquery != NULL)
-	{
-		flattenJsQueryParseItem(&buf, jsquery, false);
-
-		res = (JsQuery*)buf.data;
-		SET_VARSIZE(res, buf.len);
+	flattenJsQueryParseItem(&buf, jsquery, false);
 
-		PG_RETURN_JSQUERY(res);
-	}
+	res = (JsQuery*)buf.data;
+	SET_VARSIZE(res, buf.len);
 
-	PG_RETURN_NULL();
+	PG_RETURN_JSQUERY(res);
 }
 
 static void
diff --git a/jsquery_scan.l b/jsquery_scan.l
index 3c7f2dd..f145650 100644
--- a/jsquery_scan.l
+++ b/jsquery_scan.l
@@ -206,7 +206,7 @@ yyerror(JsQueryParseItem **result, const char *message)
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("bad jsquery representation"),
 				 /* translator: %s is typically "syntax error" */
-				 errdetail("%s at end of input", message)));
+				 errdetail("%s at the end of input", message)));
 	}
 	else
 	{
diff --git a/sql/jsquery.sql b/sql/jsquery.sql
index 0b50dbe..d183741 100644
--- a/sql/jsquery.sql
+++ b/sql/jsquery.sql
@@ -7,6 +7,7 @@ CREATE TABLE test_jsquery (v jsonb);
 
 \copy test_jsquery from 'data/test_jsquery.data'
 
+select ''::jsquery;
 select 'asd.zzz = 13'::jsquery;
 select 'asd.zzz < 13'::jsquery;
 select 'asd(zzz < 13)'::jsquery;