diff --git a/docs/schema.md b/docs/schema.md
index 567802f7..ec27cb04 100644
--- a/docs/schema.md
+++ b/docs/schema.md
@@ -29,8 +29,8 @@ For documentation, the schema allows for user comments by ignoring any text prec
 <variable-name>:<variable-pattern>
 ```
 
-* `variable-name` may contain any alphanumeric characters, but may not be the reserved names
-  `delimiters` or `timestamp`.
+* `variable-name` may contain any printable character except space and colon, but may not be the
+  reserved names `delimiters` or `timestamp`.
 * `variable-pattern` is a regular expression using the supported
   [syntax](#regular-expression-syntax).
 
diff --git a/src/log_surgeon/SchemaParser.cpp b/src/log_surgeon/SchemaParser.cpp
index 0b7816d4..41baf8ea 100644
--- a/src/log_surgeon/SchemaParser.cpp
+++ b/src/log_surgeon/SchemaParser.cpp
@@ -472,14 +472,12 @@ auto SchemaParser::add_lexical_rules() -> void {
     // RegexASTGroupByte default constructs to an m_negate group, so we add the only two characters
     // which can't be in a comment, the newline and carriage return characters as they signify the
     // end of the comment.
-    unique_ptr<RegexASTGroupByte> comment_characters = make_unique<RegexASTGroupByte>();
+    auto comment_characters{make_unique<RegexASTGroupByte>()};
     comment_characters->add_literal('\r');
     comment_characters->add_literal('\n');
     add_token_group("CommentCharacters", std::move(comment_characters));
-    add_token_group("IdentifierCharacters", make_unique<RegexASTGroupByte>('a', 'z'));
-    add_token_group("IdentifierCharacters", make_unique<RegexASTGroupByte>('A', 'Z'));
-    add_token_group("IdentifierCharacters", make_unique<RegexASTGroupByte>('0', '9'));
-    add_token("IdentifierCharacters", '_');
+    add_token_group("IdentifierCharacters", make_unique<RegexASTGroupByte>('!', ':' - 1));
+    add_token_group("IdentifierCharacters", make_unique<RegexASTGroupByte>(':' + 1, '~'));
 }
 
 auto SchemaParser::add_productions() -> void {
diff --git a/tests/test-schema.cpp b/tests/test-schema.cpp
index 8a384a51..1af4f830 100644
--- a/tests/test-schema.cpp
+++ b/tests/test-schema.cpp
@@ -1,5 +1,7 @@
 #include <string>
 #include <string_view>
+#include <utility>
+#include <vector>
 
 #include <log_surgeon/finite_automata/RegexAST.hpp>
 #include <log_surgeon/Schema.hpp>
@@ -16,8 +18,10 @@
 
 using log_surgeon::Schema;
 using log_surgeon::SchemaVarAST;
+using std::pair;
 using std::string;
 using std::string_view;
+using std::vector;
 
 using RegexASTCatByte
         = log_surgeon::finite_automata::RegexASTCat<log_surgeon::finite_automata::ByteNfaState>;
@@ -155,29 +159,64 @@ TEST_CASE("add_invalid_var_priorities", "[Schema]") {
 
 /**
  * @ingroup unit_tests_schema
- * @brief Create a schema, adding a variable and capture group name with an underscore.
+ * @brief Create a schema, adding a variable and capture group name with various character
+ * combinations that should succeed.
  */
-TEST_CASE("add_underscore_name", "[Schema]") {
+TEST_CASE("add_various_correct_variable_names", "[Schema]") {
     Schema schema;
-    string const var_name = "var_name";
-    string const cap_name = "cap_name";
-    string const var_schema = var_name + string(":a(?<") + cap_name + string(">_)b");
-    schema.add_variable(string_view(var_schema), -1);
 
-    auto const schema_ast = schema.release_schema_ast_ptr();
-    REQUIRE(schema_ast->m_schema_vars.size() == 1);
-    REQUIRE(schema.release_schema_ast_ptr()->m_schema_vars.empty());
-
-    auto& schema_var_ast_ptr = schema_ast->m_schema_vars.at(0);
-    REQUIRE(nullptr != schema_var_ast_ptr);
-    auto& schema_var_ast = dynamic_cast<SchemaVarAST&>(*schema_var_ast_ptr);
-    REQUIRE(var_name == schema_var_ast.m_name);
+    vector<pair<string, string>> name_pairs {
+            {"varName123","capName123"},
+            {"var_name","cap_name"},
+            {"var@name","cap@name"},
+            {"var.name","cap.name"},
+            {"var-name","cap-name"},
+            {"var~name","cap~name"},
+            {"var\"name\"","cap\"name\""},
+            {"var'name'","cap'name'"}
+    };
+
+    for (auto const& [var_name, cap_name] : name_pairs) {
+        string const var_schema{var_name + string(":a(?<") + cap_name + string(">_)b")};
+        schema.add_variable(string_view(var_schema), -1);
+
+        auto const schema_ast{schema.release_schema_ast_ptr()};
+        REQUIRE(schema_ast->m_schema_vars.size() == 1);
+        REQUIRE(schema.release_schema_ast_ptr()->m_schema_vars.empty());
+
+        auto& schema_var_ast_ptr{schema_ast->m_schema_vars.at(0)};
+        REQUIRE(nullptr != schema_var_ast_ptr);
+        auto& schema_var_ast{dynamic_cast<SchemaVarAST&>(*schema_var_ast_ptr)};
+        REQUIRE(var_name == schema_var_ast.m_name);
+
+        REQUIRE_NOTHROW([&]() -> void {
+            (void)dynamic_cast<RegexASTCatByte&>(*schema_var_ast.m_regex_ptr);
+        }());
+
+        auto const captures{schema_var_ast.m_regex_ptr->get_subtree_positive_captures()};
+        REQUIRE(captures.size() == 1);
+        REQUIRE(cap_name == captures.at(0)->get_name());
+    }
+}
 
-    REQUIRE_NOTHROW([&]() -> void {
-        (void)dynamic_cast<RegexASTCatByte&>(*schema_var_ast.m_regex_ptr);
-    }());
+/**
+ * @ingroup unit_tests_schema
+ * @brief Create a schema, adding a variable and capture group name with various character
+ * combinations that should throw errors.
+ */
+TEST_CASE("add_various_incorrect_variable_names", "[Schema]") {
+    Schema schema;
 
-    auto const captures{schema_var_ast.m_regex_ptr->get_subtree_positive_captures()};
-    REQUIRE(captures.size() == 1);
-    REQUIRE(cap_name == captures.at(0)->get_name());
+    vector<pair<string, string>> name_pairs {
+        {"var name","validName"},
+        {"validName","cap:name"},
+        {"validName","cap name"},
+    };
+
+    for (auto const& [var_name, cap_name] : name_pairs) {
+        CAPTURE(var_name);
+        CAPTURE(cap_name);
+        string const var_schema{var_name + string(":a(?<") + cap_name + string(">_)b")};
+        REQUIRE_THROWS(schema.add_variable(string_view(var_schema), -1));
+    }
 }