diff --git a/src/backend/utils/adt/geo_ops.c b/src/backend/utils/adt/geo_ops.c
index 8530354..0f4f763 100644
--- a/src/backend/utils/adt/geo_ops.c
+++ b/src/backend/utils/adt/geo_ops.c
@@ -974,20 +974,25 @@ line_recv(PG_FUNCTION_ARGS)
 {
 	StringInfo	buf = (StringInfo) PG_GETARG_POINTER(0);
 	LINE	   *line;
 
 	line = (LINE *) palloc(sizeof(LINE));
 
 	line->A = pq_getmsgfloat8(buf);
 	line->B = pq_getmsgfloat8(buf);
 	line->C = pq_getmsgfloat8(buf);
 
+	if (FPzero(line->A) && FPzero(line->B))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+				 errmsg("invalid line specification: A and B cannot both be zero")));
+
 	PG_RETURN_LINE_P(line);
 }
 
 /*
  *		line_send			- converts line to binary format
  */
 Datum
 line_send(PG_FUNCTION_ARGS)
 {
 	LINE	   *line = PG_GETARG_LINE_P(0);
@@ -1146,34 +1151,29 @@ line_horizontal(PG_FUNCTION_ARGS)
 	LINE	   *line = PG_GETARG_LINE_P(0);
 
 	PG_RETURN_BOOL(FPzero(line->A));
 }
 
 Datum
 line_eq(PG_FUNCTION_ARGS)
 {
 	LINE	   *l1 = PG_GETARG_LINE_P(0);
 	LINE	   *l2 = PG_GETARG_LINE_P(1);
-	double		k;
 
-	if (!FPzero(l2->A))
-		k = l1->A / l2->A;
-	else if (!FPzero(l2->B))
-		k = l1->B / l2->B;
-	else if (!FPzero(l2->C))
-		k = l1->C / l2->C;
+	if (!FPzero(l1->A))
+		PG_RETURN_BOOL(!FPzero(l2->A) &&
+					   FPeq(l1->A * l2->B, l2->A * l1->B) &&
+					   FPeq(l1->A * l2->C, l2->A * l1->C));
 	else
-		k = 1.0;
-
-	PG_RETURN_BOOL(FPeq(l1->A, k * l2->A) &&
-				   FPeq(l1->B, k * l2->B) &&
-				   FPeq(l1->C, k * l2->C));
+		PG_RETURN_BOOL(!FPzero(l2->B) &&
+					   FPeq(l1->A * l2->B, l2->A * l1->B) &&
+					   FPeq(l1->B * l2->C, l2->B * l1->C));
 }
 
 
 /*----------------------------------------------------------
  *	Line arithmetic routines.
  *---------------------------------------------------------*/
 
 /* line_distance()
  * Distance between two lines.
  */
@@ -1182,23 +1182,23 @@ line_distance(PG_FUNCTION_ARGS)
 {
 	LINE	   *l1 = PG_GETARG_LINE_P(0);
 	LINE	   *l2 = PG_GETARG_LINE_P(1);
 	float8		result;
 	Point	   *tmp;
 
 	if (!DatumGetBool(DirectFunctionCall2(line_parallel,
 										  LinePGetDatum(l1),
 										  LinePGetDatum(l2))))
 		PG_RETURN_FLOAT8(0.0);
-	if (FPzero(l1->B))			/* vertical? */
+	if (FPzero(l1->A) || FPzero(l1->B))		/* horizontal or vertical? */
 		PG_RETURN_FLOAT8(fabs(l1->C - l2->C));
-	tmp = point_construct(0.0, l1->C);
+	tmp = point_construct(0.0, -l1->C / l1->B);
 	result = dist_pl_internal(tmp, l2);
 	PG_RETURN_FLOAT8(result);
 }
 
 /* line_interpt()
  * Point where two lines l1, l2 intersect (if any)
  */
 Datum
 line_interpt(PG_FUNCTION_ARGS)
 {
@@ -2720,28 +2720,28 @@ close_pl(PG_FUNCTION_ARGS)
 	Point	   *pt = PG_GETARG_POINT_P(0);
 	LINE	   *line = PG_GETARG_LINE_P(1);
 	Point	   *result;
 	LINE	   *tmp;
 	double		invm;
 
 	result = (Point *) palloc(sizeof(Point));
 
 	if (FPzero(line->B))		/* vertical? */
 	{
-		result->x = line->C;
+		result->x = -line->C / line->A;
 		result->y = pt->y;
 		PG_RETURN_POINT_P(result);
 	}
 	if (FPzero(line->A))		/* horizontal? */
 	{
 		result->x = pt->x;
-		result->y = line->C;
+		result->y = -line->C / line->B;
 		PG_RETURN_POINT_P(result);
 	}
 	/* drop a perpendicular and find the intersection point */
 
 	/* invert and flip the sign on the slope to get a perpendicular */
 	invm = line->B / line->A;
 	tmp = line_construct_pm(pt, invm);
 	result = line_interpt_internal(tmp, line);
 	Assert(result != NULL);
 	PG_RETURN_POINT_P(result);