diff --git a/analyzer/expression.go b/analyzer/expression.go
index 832a672..1c34061 100644
--- a/analyzer/expression.go
+++ b/analyzer/expression.go
@@ -3,6 +3,7 @@ package analyzer
 import "fmt"
 import "git.tebibyte.media/fspl/fspl/errors"
 import "git.tebibyte.media/fspl/fspl/entity"
+import "git.tebibyte.media/fspl/fspl/parser/fspl"
 
 // All expression analysis routines must take in the type they are being
 // assigned to and return an error if they can't be assigned to it. if the type
@@ -62,6 +63,13 @@ func (this *Tree) analyzeDeclaration (
 	entity.Expression,
 	error,
 ) {
+	if fsplParser.IsReserved(declaration.Name) {
+		return nil, errors.Errorf (
+			declaration.Position(),
+			"cannot shadow reserved identifier %s",
+			declaration.Name)
+	}
+
 	scope, _ := this.topScope()
 	existing := scope.Variable(declaration.Name)
 	if existing != nil {
diff --git a/analyzer/tree.go b/analyzer/tree.go
index 2ff1cb3..17e6e84 100644
--- a/analyzer/tree.go
+++ b/analyzer/tree.go
@@ -76,6 +76,11 @@ func (this *Tree) assembleRawMaps () error {
 }
 
 func (this *Tree) topLevelNameAvailable (currentPos errors.Position, key entity.Key) error {
+	if fsplParser.IsReserved(key.Name) {
+		return errors.Errorf (
+			currentPos, "cannot shadow reserved identifier %s",
+			key.Name)
+	}
 	if _, isPrimitive := primitiveTypes[key.Name]; isPrimitive {
 		return errors.Errorf (
 			currentPos, "cannot shadow primitive %s",