diff --git a/internal/configs/configschema/coerce_value.go b/internal/configs/configschema/coerce_value.go
index fec6b35118..9c47257d45 100644
--- a/internal/configs/configschema/coerce_value.go
+++ b/internal/configs/configschema/coerce_value.go
@@ -67,8 +67,10 @@ func (b *Block) coerceValue(in cty.Value, path cty.Path) (cty.Value, error) {
 			val = in.GetAttr(name)
 		case attrS.Computed || attrS.Optional:
 			val = cty.NullVal(attrType)
-		default:
+		case attrS.Required:
 			return cty.UnknownVal(impliedType), path.NewErrorf("attribute %q is required", name)
+		default:
+			return cty.UnknownVal(impliedType), path.NewErrorf("attribute %q has none of required, optional, or computed set", name)
 		}
 
 		val, err := convert.Convert(val, attrConvType)
diff --git a/internal/configs/configschema/coerce_value_test.go b/internal/configs/configschema/coerce_value_test.go
index 3deeff719b..697724c6c1 100644
--- a/internal/configs/configschema/coerce_value_test.go
+++ b/internal/configs/configschema/coerce_value_test.go
@@ -446,6 +446,20 @@ func TestCoerceValue(t *testing.T) {
 			}),
 			``,
 		},
+		"omitted attribute requirements": {
+			&Block{
+				Attributes: map[string]*Attribute{
+					"foo": {
+						Type: cty.String,
+					},
+				},
+			},
+			cty.EmptyObjectVal,
+			cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.UnknownVal(cty.String),
+			}),
+			`attribute "foo" has none of required, optional, or computed set`,
+		},
 		"dynamic value attributes": {
 			&Block{
 				BlockTypes: map[string]*NestedBlock{