diff --git a/pql/ast.go b/pql/ast.go
index 2e8d31880..355b97740 100644
--- a/pql/ast.go
+++ b/pql/ast.go
@@ -795,7 +795,7 @@ type Condition struct {
 
 // String returns the string representation of the condition.
 func (cond *Condition) String() string {
-	return fmt.Sprintf("%s %s", cond.Op.String(), formatValue(cond.Value))
+	return fmt.Sprintf("%s%s", cond.Op.String(), formatValue(cond.Value))
 }
 
 // StringWithSubj returns the string representation of the condition
@@ -926,6 +926,8 @@ func (cond *Condition) StringSliceValue() ([]string, bool) {
 
 func formatValue(v interface{}) string {
 	switch v := v.(type) {
+	case nil:
+		return "null"
 	case string:
 		return fmt.Sprintf("%q", v)
 	case []interface{}:
diff --git a/pql/ast_test.go b/pql/ast_test.go
index 157b0c6bf..6e3a3d5ad 100644
--- a/pql/ast_test.go
+++ b/pql/ast_test.go
@@ -36,7 +36,7 @@ func TestCall_String(t *testing.T) {
 				"field0": &pql.Condition{Op: pql.GTE, Value: 10},
 			},
 		}
-		if s := c.String(); s != `Range(field0>= 10, other="f")` {
+		if s := c.String(); s != `Range(field0>=10, other="f")` {
 			t.Fatalf("unexpected string: %s", s)
 		}
 	})
@@ -44,18 +44,20 @@ func TestCall_String(t *testing.T) {
 
 // Ensure condition string with subject is correct.
 func TestCondition_StringWithSubj(t *testing.T) {
-	op := pql.BETWEEN
 	subj := "subj"
 	for _, tt := range []struct {
-		val []interface{}
+		op  pql.Token
+		val interface{}
 		exp string
 	}{
-		{[]interface{}{int64(4), int64(8)}, "4<=subj<=8"},
-		{[]interface{}{uint64(5), uint64(9)}, "5<=subj<=9"},
-		{[]interface{}{pql.Decimal{Value: -401, Scale: 2}, pql.Decimal{Value: 802, Scale: 1}}, "-4.01<=subj<=80.2"},
+		{pql.BETWEEN, []interface{}{int64(4), int64(8)}, "4<=subj<=8"},
+		{pql.BETWEEN, []interface{}{uint64(5), uint64(9)}, "5<=subj<=9"},
+		{pql.BETWEEN, []interface{}{pql.Decimal{Value: -401, Scale: 2}, pql.Decimal{Value: 802, Scale: 1}}, "-4.01<=subj<=80.2"},
+		{pql.EQ, nil, "subj==null"},
+		{pql.NEQ, nil, "subj!=null"},
 	} {
 		c := &pql.Condition{
-			Op:    op,
+			Op:    tt.op,
 			Value: tt.val,
 		}
 		if sws := c.StringWithSubj(subj); sws != tt.exp {
diff --git a/pql/pqlpeg_test.go b/pql/pqlpeg_test.go
index faf50056f..48eaf10c4 100644
--- a/pql/pqlpeg_test.go
+++ b/pql/pqlpeg_test.go
@@ -46,7 +46,7 @@ SetBit(Union(Zitmap(row==4), Intersect(Qitmap(blah>4), Ritmap(field="http://zoo9
 	if err != nil {
 		t.Fatalf("should have parsed: %v", err)
 	}
-	if q.String() != `TopN(Bitmap(id== "other"), _field="blah", field="f", n=0)` {
+	if q.String() != `TopN(Bitmap(id=="other"), _field="blah", field="f", n=0)` {
 		t.Fatalf("Failed, got: %s", q)
 	}
 
@@ -59,7 +59,7 @@ SetBit(Union(Zitmap(row==4), Intersect(Qitmap(blah>4), Ritmap(field="http://zoo9
 	if err != nil {
 		t.Fatalf("should have parsed: %v", err)
 	}
-	if q.String() != `Bitmap(did== "other", row=4)` {
+	if q.String() != `Bitmap(did=="other", row=4)` {
 		t.Fatalf("got %s", q)
 	}