diff --git a/src/api/api_context.cpp b/src/api/api_context.cpp
index 05e1ca675..3349bed7c 100644
--- a/src/api/api_context.cpp
+++ b/src/api/api_context.cpp
@@ -128,6 +128,7 @@ namespace api {
             for (unsigned i = 0; i < m_replay_stack.size(); ++i) {
                 dealloc(m_replay_stack[i]);
             }
+            m_ast_trail.reset();
         }
         reset_parser();
         dealloc(m_solver);
@@ -360,6 +361,7 @@ namespace api {
                 }
             }
         }
+        SASSERT(num_scopes <= get_smt_kernel().get_scope_level());
         get_smt_kernel().pop(num_scopes);
     }
 
diff --git a/src/api/api_interp.cpp b/src/api/api_interp.cpp
index 03d5ff843..e06ad5192 100644
--- a/src/api/api_interp.cpp
+++ b/src/api/api_interp.cpp
@@ -411,7 +411,7 @@ static void get_file_params(const char *filename, hash_map<std::string,std::stri
       for(unsigned i = 0; i < tokens.size(); i++){
 	std::string &tok = tokens[i];
 	size_t eqpos = tok.find('=');
-	if(eqpos >= 0 && eqpos < tok.size()){
+	if(eqpos != std::string::npos){
 	  std::string left = tok.substr(0,eqpos);
 	  std::string right = tok.substr(eqpos+1,tok.size()-eqpos-1);
 	  params[left] = right;
diff --git a/src/api/api_solver_old.cpp b/src/api/api_solver_old.cpp
index e0533fbd9..b81fb2f2c 100644
--- a/src/api/api_solver_old.cpp
+++ b/src/api/api_solver_old.cpp
@@ -40,7 +40,7 @@ extern "C" {
         LOG_Z3_pop(c, num_scopes);
         RESET_ERROR_CODE();
         CHECK_SEARCHING(c);
-        if (num_scopes > mk_c(c)->get_smt_kernel().get_scope_level()) {
+        if (num_scopes > mk_c(c)->get_num_scopes()) {
             SET_ERROR_CODE(Z3_IOB);
             return;
         }
diff --git a/src/api/python/z3.py b/src/api/python/z3.py
index 50d29a790..d46d40ab2 100644
--- a/src/api/python/z3.py
+++ b/src/api/python/z3.py
@@ -6960,7 +6960,7 @@ def substitute(t, *m):
     if isinstance(m, tuple):
         m1 = _get_args(m)
         if isinstance(m1, list):
-            m = _get_args(m1)
+            m = m1
     if __debug__:
         _z3_assert(is_expr(t), "Z3 expression expected")
         _z3_assert(all([isinstance(p, tuple) and is_expr(p[0]) and is_expr(p[1]) and p[0].sort().eq(p[1].sort()) for p in m]), "Z3 invalid substitution, expression pairs expected.")
diff --git a/src/api/z3_api.h b/src/api/z3_api.h
index 4ffdfa9c2..e1c42667a 100644
--- a/src/api/z3_api.h
+++ b/src/api/z3_api.h
@@ -7069,7 +7069,7 @@ END_MLAPI_EXCLUDE
        \mlonly then a valid model is returned.  Otherwise, it is unsafe to use the returned model.\endmlonly
        \conly The caller is responsible for deleting the model using the function #Z3_del_model.
        
-       \conly \remark In constrast with the rest of the Z3 API, the reference counter of the
+       \conly \remark In contrast with the rest of the Z3 API, the reference counter of the
        \conly model is incremented. This is to guarantee backward compatibility. In previous
        \conly versions, models did not support reference counting.
        
@@ -7182,6 +7182,11 @@ END_MLAPI_EXCLUDE
        \brief Delete a model object.
        
        \sa Z3_check_and_get_model
+
+       \conly \remark The Z3_check_and_get_model automatically increments a reference count on the model.
+       \conly The expected usage is that models created by that method are deleted using Z3_del_model.
+       \conly This is for backwards compatibility and in contrast to the rest of the API where
+       \conly callers are responsible for managing reference counts.
     
        \deprecated Subsumed by Z3_solver API
        
diff --git a/src/smt/smt_model_checker.cpp b/src/smt/smt_model_checker.cpp
index 526447f9f..7053d63ec 100644
--- a/src/smt/smt_model_checker.cpp
+++ b/src/smt/smt_model_checker.cpp
@@ -136,9 +136,8 @@ namespace smt {
         if (cex == 0)
             return false; // no model available.
         unsigned num_decls = q->get_num_decls();
-        unsigned   num_sks = sks.size();
         // Remark: sks were created for the flat version of q.
-        SASSERT(num_sks >= num_decls); 
+        SASSERT(sks.size() >= num_decls);
         expr_ref_buffer bindings(m_manager);
         bindings.resize(num_decls);
         unsigned max_generation = 0;