diff --git a/src/libOpenImageIO/exif.cpp b/src/libOpenImageIO/exif.cpp
index 10b75c21..0287d9c5 100644
--- a/src/libOpenImageIO/exif.cpp
+++ b/src/libOpenImageIO/exif.cpp
@@ -213,6 +213,9 @@ static const EXIF_tag_info exif_tag_table[] = {
 
 
 
+// libtiff > 4.1.0 defines these in tiff.h. For older libtiff, let's define
+// them ourselves.
+#ifndef GPSTAG_VERSIONID
 enum GPSTag {
     GPSTAG_VERSIONID = 0, 
     GPSTAG_LATITUDEREF = 1,  GPSTAG_LATITUDE = 2,
@@ -237,6 +240,7 @@ enum GPSTag {
     GPSTAG_DIFFERENTIAL = 30,
     GPSTAG_HPOSITIONINGERROR = 31
 };
+#endif
 
 static const EXIF_tag_info gps_tag_table[] = {
     { GPSTAG_VERSIONID,		"GPS:VersionID",	TIFF_BYTE, 4 }, 
@@ -270,7 +274,7 @@ static const EXIF_tag_info gps_tag_table[] = {
     { GPSTAG_AREAINFORMATION,	"GPS:AreaInformation",	TIFF_UNDEFINED, 1 },
     { GPSTAG_DATESTAMP,		"GPS:DateStamp",	TIFF_ASCII, 0 },
     { GPSTAG_DIFFERENTIAL,	"GPS:Differential",	TIFF_SHORT, 1 },
-    { GPSTAG_HPOSITIONINGERROR,	"GPS:HPositioningError",TIFF_RATIONAL, 1 },
+    { GPSTAG_GPSHPOSITIONINGERROR,     "GPS:HPositioningError",TIFF_RATIONAL, 1 },
     { -1, NULL }  // signal end of table
 };