diff --git a/minisql/src/type_system.rs b/minisql/src/type_system.rs
index 8b95d7b..27a632b 100644
--- a/minisql/src/type_system.rs
+++ b/minisql/src/type_system.rs
@@ -30,6 +30,18 @@ pub enum IndexableValue {
     // TODO: what about null?
 }
 
+impl DbType {
+    pub fn is_indexable(&self) -> bool {
+        match self {
+            Self::String => true,
+            Self::Int => true,
+            Self::Number => false,
+            Self::Uuid => true,
+        }
+    }
+
+}
+
 impl Value {
     pub fn to_type(&self) -> DbType {
         match self {
diff --git a/parser/src/validation.rs b/parser/src/validation.rs
index b36ce55..b818448 100644
--- a/parser/src/validation.rs
+++ b/parser/src/validation.rs
@@ -20,6 +20,8 @@ pub enum ValidationError {
     PrimaryKeyMissing(TableName),
     #[error("multiple primary keys found in table {0}")]
     MultiplePrimaryKeysFound(TableName),
+    #[error("attempt to index non-indexable column {1} in table {0}")]
+    AttemptToIndexNonIndexableColumn(TableName, ColumnName),
     #[error("type mismatch at column `{column_name:?}` (expected {expected_type:?}, found {received_type:?})")]
     TypeMismatch {
         column_name: ColumnName,
@@ -202,13 +204,18 @@ fn validate_condition(condition: Option<syntax::Condition>, schema: &TableSchema
 }
 
 fn validate_create_index(table_name: TableName, column_name: ColumnName, db_schema: &DbSchema) -> Result<Operation, ValidationError> {
-    // TODO: You should disallow indexing of Number columns.
     let (table_position, schema) = validate_table_exists(db_schema, &table_name)?;
     schema
-        .get_column_position(&column_name)
+        .get_column(&column_name)
         .map_or_else(
             || Err(ValidationError::ColumnsDoNotExist(vec![column_name.to_string()])),
-            |column| Ok(Operation::CreateIndex(table_position, column))
+            |(column, type_)| {
+                if type_.is_indexable() {
+                    Ok(Operation::CreateIndex(table_position, column))
+                } else {
+                    Err(ValidationError::AttemptToIndexNonIndexableColumn(column_name.clone(), table_name))
+                }
+            }
         )
 }