diff --git a/lib/exec.c b/lib/exec.c
index fed6651..802cd4f 100644
--- a/lib/exec.c
+++ b/lib/exec.c
@@ -3559,10 +3559,12 @@ static int execute (hcl_t* hcl)
 					/* store or pop */
 					if (HCL_IS_CLASS(hcl, ass->cdr) && ((hcl_oop_class_t)ass->cdr)->name == ass->car)
 					{
+						/* the existing value must be a class. disallow re-definition */
 						hcl_seterrbfmt (hcl, HCL_EPERM, "prohibited redefintion of %.*js", HCL_OBJ_GET_SIZE(ass->car), HCL_OBJ_GET_CHAR_SLOT(ass->car));
 						if (do_throw_with_internal_errmsg(hcl, fetched_instruction_pointer) >= 0) break;
 						goto oops_with_errmsg_supplement;
 					}
+
 					ass->cdr = HCL_STACK_GETTOP(hcl);
 
 					if ((bcode >> 2) & 1)
diff --git a/t/class-5001.err b/t/class-5001.err
index 7820cd4..d9d9e9b 100644
--- a/t/class-5001.err
+++ b/t/class-5001.err
@@ -147,3 +147,41 @@ class X [ a b c ] {
 		}
 	}
 }
+
+---
+
+class F {
+}
+
+class F { ##ERROR: exception not handled - "prohibited redefintion of F
+}
+
+---
+
+class F {
+}
+
+F := 30 ##ERROR: exception not handled - "prohibited redefintion of F
+
+---
+
+
+class F {
+}
+
+F := (class { ##ERROR: exception not handled - "prohibited redefintion of F"
+})
+
+---
+
+F := (class {
+})
+
+F := (class F { ##ERROR: exception not handle - "prohibited redefintion of F"
+})
+
+##  TDOO: do we need to allow the above?
+
+##F := 30
+##class F { ##ERROR: exception not handled - "prohibited redefintion of F"
+##}