diff --git a/src/api/api_ast.cpp b/src/api/api_ast.cpp
index 4f4da6bd4..52be66e77 100644
--- a/src/api/api_ast.cpp
+++ b/src/api/api_ast.cpp
@@ -895,7 +895,7 @@ extern "C" {
         RESET_ERROR_CODE();
         func_decl* _d = to_func_decl(d);
 
-        if (null_family_id == _d->get_family_id()) {
+        if (d == nullptr || null_family_id == _d->get_family_id()) {
             return Z3_OP_UNINTERPRETED;
         }
         if (mk_c(c)->get_basic_fid() == _d->get_family_id()) {
diff --git a/src/smt/theory_bv.cpp b/src/smt/theory_bv.cpp
index e693c4531..a9b3e6131 100644
--- a/src/smt/theory_bv.cpp
+++ b/src/smt/theory_bv.cpp
@@ -850,6 +850,7 @@ namespace smt {
     }
 
     bool theory_bv::internalize_term(app * term) {
+        try {
         SASSERT(term->get_family_id() == get_family_id());
         TRACE("bv", tout << "internalizing term: " << mk_bounded_pp(term, get_manager()) << "\n";);
         if (approximate_term(term)) {
@@ -907,6 +908,11 @@ namespace smt {
             UNREACHABLE();
             return false;
         }
+        }
+        catch (z3_exception& ex) {
+            IF_VERBOSE(1, verbose_stream() << ex.msg() << "\n";);
+            throw;
+        }
     }
 
 #define MK_NO_OVFL(NAME, OP)                                                                                    \