diff --git a/src/runtime/c/pgf/parser.cxx b/src/runtime/c/pgf/parser.cxx
index 6751aec75..1cf30185d 100644
--- a/src/runtime/c/pgf/parser.cxx
+++ b/src/runtime/c/pgf/parser.cxx
@@ -1676,11 +1676,15 @@ bool PgfParser::change(size_t i, PgfText *change)
         allocated_size = new_allocated_size;
     }
 
-    const uint8_t *ptr1 =
-        (prev_state!=NULL)
-            ? (uint8_t *) &sentence->text[prev_state->start.byte_pos]
-            : NULL;
-    size_t pos = prev_state->start.pos;
+    size_t pos;
+    const uint8_t *ptr1;
+    if (prev_state!=NULL) {
+        ptr1 = (uint8_t *) &sentence->text[prev_state->start.byte_pos];
+        pos  = prev_state->start.pos;
+    } else {
+        ptr1 = (uint8_t *) sentence->text;
+        pos  = 0;
+    }
     while (pos < update_new_pos) {
         pgf_utf8_decode(&ptr1); pos++;
     }