diff --git a/src/ast/rewriter/seq_axioms.cpp b/src/ast/rewriter/seq_axioms.cpp
index b7c0b7186..22114aecc 100644
--- a/src/ast/rewriter/seq_axioms.cpp
+++ b/src/ast/rewriter/seq_axioms.cpp
@@ -1243,7 +1243,7 @@ namespace seq {
         else if (seq.str.is_extract(x, y, offs, l)) {
             // len(extract(y, o, l)) = l if len(y) >= o + l, o >= 0, l >= 0
             // len(extract(y, o, l)) = 0 if o < 0 or l <= 0 or len(y) < o
-            // len(extract(y, o, l)) = o + l - len(y) if o <= len(y) < o + l
+            // len(extract(y, o, l)) = len(y) - o if o <= len(y) < o + l
             expr_ref len_y(mk_len(y), m);
             expr_ref z(a.mk_int(0), m);
             expr_ref y_ge_l = mk_ge(a.mk_sub(len_y, a.mk_add(offs, l)), 0);
@@ -1255,7 +1255,7 @@ namespace seq {
             add_clause(offs_ge_0, mk_eq(n, z));
             add_clause(l_ge_0, mk_eq(n, z));
             add_clause(y_ge_o, mk_eq(n, z));
-            add_clause(~y_ge_o, y_ge_l, mk_eq(n, a.mk_sub(a.mk_add(offs, l), len_y))); 
+            add_clause(~y_ge_o, y_ge_l, mk_eq(n, a.mk_sub(len_y, offs))); 
         }
         else if (seq.str.is_unit(x) ||
             seq.str.is_empty(x) ||