diff --git a/src/api/api_ast_map.cpp b/src/api/api_ast_map.cpp
index 72bf0d7a8..714712faf 100644
--- a/src/api/api_ast_map.cpp
+++ b/src/api/api_ast_map.cpp
@@ -53,7 +53,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_ast_map_dec_ref(c, m);
         RESET_ERROR_CODE();
-        to_ast_map(m)->dec_ref();
+        if (m)
+            to_ast_map(m)->dec_ref();
         Z3_CATCH;
     }
 
diff --git a/src/api/api_datalog.cpp b/src/api/api_datalog.cpp
index 6bf5af0e6..224e86b89 100644
--- a/src/api/api_datalog.cpp
+++ b/src/api/api_datalog.cpp
@@ -243,7 +243,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_fixedpoint_dec_ref(c, s);
         RESET_ERROR_CODE();
-        to_fixedpoint(s)->dec_ref();
+        if (s)
+            to_fixedpoint(s)->dec_ref();
         Z3_CATCH;
     }
 
diff --git a/src/api/api_goal.cpp b/src/api/api_goal.cpp
index a9dddd6f2..7e2b5cd55 100644
--- a/src/api/api_goal.cpp
+++ b/src/api/api_goal.cpp
@@ -53,7 +53,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_goal_dec_ref(c, g);
         RESET_ERROR_CODE();
-        to_goal(g)->dec_ref();
+        if (g)
+            to_goal(g)->dec_ref();
         Z3_CATCH;
     }
 
diff --git a/src/api/api_opt.cpp b/src/api/api_opt.cpp
index e20c78738..7b5ba7467 100644
--- a/src/api/api_opt.cpp
+++ b/src/api/api_opt.cpp
@@ -68,7 +68,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_optimize_dec_ref(c, o);
         RESET_ERROR_CODE();
-        to_optimize(o)->dec_ref();
+        if (o)
+            to_optimize(o)->dec_ref();
         Z3_CATCH;
     }
     
diff --git a/src/api/api_params.cpp b/src/api/api_params.cpp
index 866687b7e..d17018638 100644
--- a/src/api/api_params.cpp
+++ b/src/api/api_params.cpp
@@ -55,7 +55,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_params_dec_ref(c, p);
         RESET_ERROR_CODE();
-        to_params(p)->dec_ref();
+        if (p)
+            to_params(p)->dec_ref();
         Z3_CATCH;
     }
 
diff --git a/src/api/api_solver.cpp b/src/api/api_solver.cpp
index 577ff934c..6d6f01ddb 100644
--- a/src/api/api_solver.cpp
+++ b/src/api/api_solver.cpp
@@ -402,7 +402,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_solver_dec_ref(c, s);
         RESET_ERROR_CODE();
-        to_solver(s)->dec_ref();
+        if (s)
+            to_solver(s)->dec_ref();
         Z3_CATCH;
     }
 
diff --git a/src/api/api_stats.cpp b/src/api/api_stats.cpp
index 0278d7d31..01b521ed6 100644
--- a/src/api/api_stats.cpp
+++ b/src/api/api_stats.cpp
@@ -49,7 +49,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_stats_dec_ref(c, s);
         RESET_ERROR_CODE();
-        to_stats(s)->dec_ref();
+        if (s)
+            to_stats(s)->dec_ref();
         Z3_CATCH;
     }
     
diff --git a/src/api/api_tactic.cpp b/src/api/api_tactic.cpp
index 7314c9b60..adaa1f8e1 100644
--- a/src/api/api_tactic.cpp
+++ b/src/api/api_tactic.cpp
@@ -74,7 +74,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_tactic_dec_ref(c, t);
         RESET_ERROR_CODE();
-        to_tactic(t)->dec_ref();
+        if (t)
+            to_tactic(t)->dec_ref();
         Z3_CATCH;
     }
 
@@ -104,7 +105,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_probe_dec_ref(c, p);
         RESET_ERROR_CODE();
-        to_probe(p)->dec_ref();
+        if (p)
+            to_probe(p)->dec_ref();
         Z3_CATCH;
     }
 
@@ -476,7 +478,8 @@ extern "C" {
         Z3_TRY;
         LOG_Z3_apply_result_dec_ref(c, r);
         RESET_ERROR_CODE();
-        to_apply_result(r)->dec_ref();
+        if (r)
+            to_apply_result(r)->dec_ref();
         Z3_CATCH;
     }