diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 23e11b9d..21cb03c2 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-08  Mark Wielaard  <mark@klomp.org>
+
+	* dwarf_get_units.c (dwarf_get_units): Handle existing error, no
+	dwarf.
+
 2018-06-08  Mark Wielaard  <mark@klomp.org>
 
 	* dwarf_getlocation.c (store_implicit_value): Return error when
diff --git a/libdw/dwarf_get_units.c b/libdw/dwarf_get_units.c
index aece17ef..6215bf4b 100644
--- a/libdw/dwarf_get_units.c
+++ b/libdw/dwarf_get_units.c
@@ -40,6 +40,10 @@ dwarf_get_units (Dwarf *dwarf, Dwarf_CU *cu, Dwarf_CU **next_cu,
 		 Dwarf_Half *version, uint8_t *unit_type,
 		 Dwarf_Die *cudie, Dwarf_Die *subdie)
 {
+  /* Handle existing error.  */
+  if (dwarf == NULL)
+    return -1;
+
   Dwarf_Off off;
   bool v4type;
   if (cu == NULL)