diff -up tests/test_partial_loader.c.old tests/test_partial_loader.c
--- tests/test_partial_loader.c.old	2020-08-19 14:49:19.309503731 +0200
+++ tests/test_partial_loader.c	2020-08-19 14:57:45.759371679 +0200
@@ -64,14 +64,14 @@ static struct handlebars_string * execut
     // Check error
     if( handlebars_error_num(ctx) != HANDLEBARS_SUCCESS ) {
         // @todo maybe check message
-        ck_abort_msg(handlebars_error_msg(ctx));
+        ck_abort_msg("%s", handlebars_error_msg(ctx));
         goto done;
     }
 
     // Compile
     handlebars_compiler_compile(compiler, parser->program);
     if( handlebars_error_num(ctx) != HANDLEBARS_SUCCESS ) {
-        ck_abort_msg(handlebars_error_msg(ctx));
+        ck_abort_msg("%s", handlebars_error_msg(ctx));
         goto done;
     }
 
@@ -97,7 +97,7 @@ static struct handlebars_string * execut
     // Execute
     handlebars_vm_execute(vm, module, context);
 
-    ck_assert_msg(handlebars_error_msg(HBSCTX(vm)) == NULL, handlebars_error_msg(HBSCTX(vm)));
+    ck_assert_msg("%s", handlebars_error_msg(HBSCTX(vm)) == NULL, handlebars_error_msg(HBSCTX(vm)));
 
     retval = talloc_steal(NULL, vm->buffer);
 
diff -up tests/test_spec_handlebars.c.old tests/test_spec_handlebars.c
--- tests/test_spec_handlebars.c.old	2020-08-19 15:02:14.938770019 +0200
+++ tests/test_spec_handlebars.c	2020-08-19 15:08:17.911897696 +0200
@@ -333,7 +333,7 @@ START_TEST(test_ast_to_string_on_handleb
 
     // Check error
     if( handlebars_error_num(ctx) != HANDLEBARS_SUCCESS ) {
-        ck_assert_msg(0, handlebars_error_msg(ctx));
+        ck_assert_msg(0, "%s", handlebars_error_msg(ctx));
     }
 
     ast_str = handlebars_ast_to_string(ctx, parser->program);
@@ -345,7 +345,7 @@ START_TEST(test_ast_to_string_on_handleb
                                                    "" /*test->suite_name*/,
                                                    test->description, test->it, test->flags,
                                                    test->tmpl, expected, actual);
-        ck_abort_msg(tmp);
+        ck_abort_msg("%s", tmp);
     }
 
 done:
@@ -447,7 +447,7 @@ static inline void run_test(struct gener
     // Check error
     if( handlebars_error_num(ctx) != HANDLEBARS_SUCCESS ) {
         // @todo maybe check message
-        ck_assert_msg(test->exception, handlebars_error_msg(ctx));
+        ck_assert_msg(test->exception, "%s", handlebars_error_msg(ctx));
         goto done;
     }
 
@@ -560,14 +560,14 @@ static inline void run_test(struct gener
             if( 0 == regex_compare(tmp, handlebars_error_msg(HBSCTX(vm)), &regex_error) ) {
                 // ok
             } else {
-                ck_assert_msg(0, regex_error);
+                ck_assert_msg(0, "%s", regex_error);
             }
             free(tmp);
         } else {
             ck_assert_str_eq(test->message, handlebars_error_msg(HBSCTX(vm)));
         }
     } else {
-        ck_assert_msg(handlebars_error_msg(HBSCTX(vm)) == NULL, handlebars_error_msg(HBSCTX(vm)));
+        ck_assert_msg(handlebars_error_msg(HBSCTX(vm)) == NULL, "%s", handlebars_error_msg(HBSCTX(vm)));
         ck_assert_ptr_ne(test->expected, NULL);
         ck_assert_ptr_ne(vm->buffer, NULL);
 
@@ -577,7 +577,7 @@ static inline void run_test(struct gener
                                                    "" /*test->suite_name*/,
                                                    test->description, test->it, test->flags,
                                                    test->tmpl, test->expected, vm->buffer->val);
-            ck_abort_msg(tmp);
+            ck_abort_msg("%s", tmp);
         }
     }
 
diff -up tests/test_spec_handlebars_compiler.c.old tests/test_spec_handlebars_compiler.c
--- tests/test_spec_handlebars_compiler.c.old	2020-08-19 15:01:47.311831778 +0200
+++ tests/test_spec_handlebars_compiler.c	2020-08-19 15:02:01.241800639 +0200
@@ -697,7 +697,7 @@ START_TEST(handlebars_spec_compiler)
                 test->suite_name,
                 test->description, test->it, test->flags,
                 test->tmpl, test->expected->val, actual->val);
-            ck_abort_msg(tmp);
+            ck_abort_msg("%s", tmp);
         }
     /* } */
 
diff -up tests/test_spec_handlebars_parser.c.old tests/test_spec_handlebars_parser.c
--- tests/test_spec_handlebars_parser.c.old	2020-08-19 15:00:06.471057182 +0200
+++ tests/test_spec_handlebars_parser.c	2020-08-19 15:01:31.612866873 +0200
@@ -209,7 +209,7 @@ START_TEST(handlebars_spec_parser)
                 if( 0 == regex_compare(tmp, errmsgjs, &regex_error) ) {
                     // ok
                 } else {
-                    ck_assert_msg(0, regex_error);
+                    ck_assert_msg(0, "%s", regex_error);
                 }
                 free(tmp);
             } else {
@@ -222,7 +222,7 @@ START_TEST(handlebars_spec_parser)
             lesigh = handlebars_talloc_strdup_append(lesigh, errmsg);
             lesigh = handlebars_talloc_strdup_append(lesigh, "\nTemplate: \n");
             lesigh = handlebars_talloc_strdup_append(lesigh, test->tmpl);
-            ck_assert_msg(0, lesigh);
+            ck_assert_msg(0, "%s", lesigh);
         }
     } else {
         struct handlebars_string * output = handlebars_ast_print(HBSCTX(parser), parser->program);
@@ -238,10 +238,10 @@ START_TEST(handlebars_spec_parser)
                 lesigh = handlebars_talloc_strdup_append(lesigh, output->val);
                 lesigh = handlebars_talloc_strdup_append(lesigh, "\nTemplate: \n");
                 lesigh = handlebars_talloc_strdup_append(lesigh, test->tmpl);
-                ck_assert_msg(0, lesigh);
+                ck_assert_msg(0, "%s", lesigh);
             }
         } else {
-            ck_assert_msg(0, test->message);
+            ck_assert_msg(0, "%s", test->message);
         }
         
         handlebars_talloc_free(output);
diff -up tests/test_spec_mustache.c.old tests/test_spec_mustache.c
--- tests/test_spec_mustache.c.old	2020-08-19 15:09:13.225763729 +0200
+++ tests/test_spec_mustache.c	2020-08-19 15:10:04.588639326 +0200
@@ -258,7 +258,7 @@ START_TEST(test_ast_to_string_on_mustach
 
     // Check error
     if( handlebars_error_num(ctx) != HANDLEBARS_SUCCESS ) {
-        ck_assert_msg(0, handlebars_error_msg(ctx));
+        ck_assert_msg(0, "%s", handlebars_error_msg(ctx));
     }
 
     ast_str = handlebars_ast_to_string(ctx, parser->program);
@@ -271,7 +271,7 @@ START_TEST(test_ast_to_string_on_mustach
                                                "" /*test->suite_name*/,
                                                test->name, test->desc, test->flags,
                                                test->tmpl, expected, actual);
-        ck_abort_msg(tmp);
+        ck_abort_msg("%s", tmp);
     }
 
 done:
@@ -322,7 +322,7 @@ START_TEST(test_mustache_spec)
 
     // Check error
     if( handlebars_error_num(ctx) != HANDLEBARS_SUCCESS ) {
-        ck_assert_msg(0, handlebars_error_msg(ctx));
+        ck_assert_msg(0, "%s", handlebars_error_msg(ctx));
     }
 
     // Compile
@@ -330,7 +330,7 @@ START_TEST(test_mustache_spec)
     handlebars_compiler_compile(compiler, parser->program);
 
     if( handlebars_error_num(ctx) != HANDLEBARS_SUCCESS ) {
-        ck_assert_msg(0, handlebars_error_msg(ctx));
+        ck_assert_msg(0, "%s", handlebars_error_msg(ctx));
     }
 
     // Serialize
@@ -368,7 +368,7 @@ START_TEST(test_mustache_spec)
 
     // Check error
     if( handlebars_error_num(ctx) != HANDLEBARS_SUCCESS ) {
-        ck_assert_msg(0, handlebars_error_msg(ctx));
+        ck_assert_msg(0, "%s", handlebars_error_msg(ctx));
     }
 
     ck_assert_ptr_ne(vm->buffer, NULL);
@@ -379,7 +379,7 @@ START_TEST(test_mustache_spec)
                                                "" /*test->suite_name*/,
                                                test->name, test->desc, test->flags,
                                                test->tmpl, test->expected, vm->buffer->val);
-        ck_abort_msg(tmp);
+        ck_abort_msg("%s", tmp);
     }
 
     handlebars_context_dtor(ctx);
diff -up tests/test_value.c.old tests/test_value.c
--- tests/test_value.c.old	2020-08-19 14:58:55.777215189 +0200
+++ tests/test_value.c	2020-08-19 14:59:35.199127077 +0200
@@ -434,7 +434,7 @@ START_TEST(test_json_parse_error)
     if( handlebars_setjmp_ex(context, &buf) ) {
         char * error = NULL;
         if( 0 != regex_compare("^JSON Parse error", handlebars_error_msg(context), &error) ) {
-            ck_abort_msg(error);
+            ck_abort_msg("%s", error);
         }
         return;
     }
@@ -451,7 +451,7 @@ START_TEST(test_yaml_parse_error)
     if( handlebars_setjmp_ex(context, &buf) ) {
         char * error = NULL;
         if( 0 != regex_compare("^YAML Parse Error", handlebars_error_msg(context), &error) ) {
-            ck_abort_msg(error);
+            ck_abort_msg("%s", error);
         }
         return;
     }