diff --git a/src/ast/ast.cpp b/src/ast/ast.cpp
index 640bc7ceb..bdf1c18db 100644
--- a/src/ast/ast.cpp
+++ b/src/ast/ast.cpp
@@ -922,6 +922,7 @@ void basic_decl_plugin::finalize() {
     DEC_REF(m_and_decl);
     DEC_REF(m_or_decl);
     DEC_REF(m_not_decl);
+    DEC_REF(m_interp_decl);
     DEC_REF(m_iff_decl);
     DEC_REF(m_xor_decl);
     DEC_REF(m_implies_decl);
diff --git a/src/util/mpn.h b/src/util/mpn.h
index f995004c2..219368de3 100644
--- a/src/util/mpn.h
+++ b/src/util/mpn.h
@@ -101,7 +101,7 @@ private:
     bool div_n(mpn_sbuffer & numer, mpn_sbuffer const & denom,
                mpn_digit * quot, mpn_digit * rem);
 
-    #ifdef _DEBUG
+    #ifdef Z3DEBUG
     mutable char char_buf[4096];
     bool trace_enabled;
     #endif