diff --git a/polly/lib/CodeGen/IslNodeBuilder.cpp b/polly/lib/CodeGen/IslNodeBuilder.cpp
--- a/polly/lib/CodeGen/IslNodeBuilder.cpp
+++ b/polly/lib/CodeGen/IslNodeBuilder.cpp
@@ -148,14 +148,12 @@
 
 /// Return true if a return value of Predicate is true for the value represented
 /// by passed isl_ast_expr_int.
-static bool checkIslAstExprInt(__isl_take isl_ast_expr *Expr,
+static bool checkIslAstExprInt(isl::ast_expr Expr,
                                isl_bool (*Predicate)(__isl_keep isl_val *)) {
-  if (isl_ast_expr_get_type(Expr) != isl_ast_expr_int) {
-    isl_ast_expr_free(Expr);
+  if (isl_ast_expr_get_type(Expr.get()) != isl_ast_expr_int) {
     return false;
   }
-  auto ExprVal = isl_ast_expr_get_val(Expr);
-  isl_ast_expr_free(Expr);
+  auto ExprVal = isl_ast_expr_get_val(Expr.get());
   if (Predicate(ExprVal) != isl_bool_true) {
     isl_val_free(ExprVal);
     return false;
@@ -187,10 +185,10 @@
   }
 
   isl::ast_expr Init = For.init();
-  if (!checkIslAstExprInt(Init.release(), isl_val_is_zero))
+  if (!checkIslAstExprInt(Init, isl_val_is_zero))
     return -1;
   isl::ast_expr Inc = For.inc();
-  if (!checkIslAstExprInt(Inc.release(), isl_val_is_one))
+  if (!checkIslAstExprInt(Inc, isl_val_is_one))
     return -1;
   CmpInst::Predicate Predicate;
   isl::ast_expr UB = getUpperBound(For, Predicate);