diff --git a/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java b/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java
index e591a986b..f367459e2 100644
--- a/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java
+++ b/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java
@@ -240,9 +240,9 @@ public class TestSymbolIssues extends BaseJavaToolTest {
 			"mode MODE1;\n" +
 			"MODE1_TOKEN: 'qwer';",
 
-			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): L.g4:4:22: rule TOKEN contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n" +
-			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): L.g4:4:41: rule TOKEN contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n" +
-			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): L.g4:4:54: rule TOKEN contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n"
+			"error(" + ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_TOKEN_NAME.code + "): L.g4:4:22: CHANNEL1 is not a recognized token name\n" +
+			"error(" + ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_CHANNEL_NAME.code + "): L.g4:4:41: MODE1 is not a recognized channel name\n" +
+			"error(" + ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_MODE_NAME.code + "): L.g4:4:54: TOKEN1 is not a recognized mode name\n"
 		};
 
 		testErrors(test, false);
diff --git a/tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java b/tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java
index c22d170ac..220d748e1 100644
--- a/tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java
+++ b/tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java
@@ -657,8 +657,8 @@ public class TestToolSyntaxErrors extends BaseJavaToolTest {
 			"WHITESPACE: [ \\t]+      -> channel(WHITESPACE_CHANNEL);\n";
 
 		String expected =
-			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): T.g4:10:35: rule COMMENT contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n" +
-			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): T.g4:11:35: rule WHITESPACE contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n" +
+			"error(" + ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_CHANNEL_NAME.code + "): T.g4:10:35: COMMENT_CHANNEL is not a recognized channel name\n" +
+			"error(" + ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_CHANNEL_NAME.code + "): T.g4:11:35: WHITESPACE_CHANNEL is not a recognized channel name\n" +
 			"error(" + ErrorType.CHANNELS_BLOCK_IN_COMBINED_GRAMMAR.code + "): T.g4:3:0: custom channels are not supported in combined grammars\n";
 
 		String[] pair = { grammar, expected };
@@ -686,7 +686,7 @@ public class TestToolSyntaxErrors extends BaseJavaToolTest {
 
 		// WHITESPACE_CHANNEL and COMMENT_CHANNEL are defined, but NEWLINE_CHANNEL is not
 		String expected =
-			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): T.g4:10:34: rule NEWLINE contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n";
+			"error(" + ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_CHANNEL_NAME.code + "): T.g4:10:34: NEWLINE_CHANNEL is not a recognized channel name\n";
 
 		String[] pair = { grammar, expected };
 		super.testErrors(pair, true);
diff --git a/tool/src/org/antlr/v4/automata/LexerATNFactory.java b/tool/src/org/antlr/v4/automata/LexerATNFactory.java
index 979d8d3ab..e1ce57436 100644
--- a/tool/src/org/antlr/v4/automata/LexerATNFactory.java
+++ b/tool/src/org/antlr/v4/automata/LexerATNFactory.java
@@ -470,7 +470,12 @@ public class LexerATNFactory extends ParserATNFactory {
 			return null;
 		}
 
-		return tryParseInt(modeName, token);
+		try {
+			return Integer.parseInt(modeName);
+		} catch (NumberFormatException ex) {
+			g.tool.errMgr.grammarError(ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_MODE_NAME, g.fileName, token, token.getText());
+			return null;
+		}
 	}
 
 	private Integer getTokenConstantValue(String tokenName, Token token) {
@@ -491,7 +496,12 @@ public class LexerATNFactory extends ParserATNFactory {
 			return null;
 		}
 
-		return tryParseInt(tokenName, token);
+		try {
+			return Integer.parseInt(tokenName);
+		} catch (NumberFormatException ex) {
+			g.tool.errMgr.grammarError(ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_TOKEN_NAME, g.fileName, token, token.getText());
+			return null;
+		}
 	}
 
 	private Integer getChannelConstantValue(String channelName, Token token) {
@@ -515,14 +525,10 @@ public class LexerATNFactory extends ParserATNFactory {
 			return channelValue;
 		}
 
-		return tryParseInt(channelName, token);
-	}
-
-	private Integer tryParseInt(String name, Token token) {
 		try {
-			return Integer.parseInt(name);
+			return Integer.parseInt(channelName);
 		} catch (NumberFormatException ex) {
-			g.tool.errMgr.grammarError(ErrorType.UNKNOWN_LEXER_CONSTANT, g.fileName, token, currentRule.name, token != null ? token.getText() : null);
+			g.tool.errMgr.grammarError(ErrorType.CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_CHANNEL_NAME, g.fileName, token, token.getText());
 			return null;
 		}
 	}
diff --git a/tool/src/org/antlr/v4/tool/ErrorType.java b/tool/src/org/antlr/v4/tool/ErrorType.java
index 28f78f90f..c5db57763 100644
--- a/tool/src/org/antlr/v4/tool/ErrorType.java
+++ b/tool/src/org/antlr/v4/tool/ErrorType.java
@@ -1011,6 +1011,30 @@ public enum ErrorType {
 	 * <pre>C: 'test' '';</pre>
 	 */
 	EMPTY_STRINGS_NOT_ALLOWED(174, "string literals cannot be empty", ErrorSeverity.ERROR),
+	/**
+	 * Compiler Error 175.
+	 *
+	 * <p><em>name</em> is not a recognized token name</p>
+	 *
+	 * <pre>TOKEN: 'a' -> type(CHANNEL1); // error 175</pre>
+	 */
+	CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_TOKEN_NAME(175, "<arg> is not a recognized token name", ErrorSeverity.ERROR),
+	/**
+	 * Compiler Error 176.
+	 *
+	 * <p><em>name</em>is not a recognized mode name</p>
+	 *
+	 * <pre>TOKEN: 'a' -> channel(MODE1); // error 176</pre>
+	 */
+	CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_MODE_NAME(176, "<arg> is not a recognized mode name", ErrorSeverity.ERROR),
+	/**
+	 * Compiler Error 177.
+	 *
+	 * <p><em>name</em> is not a recognized channel name</p>
+	 *
+	 * <pre>TOKEN: 'a' -> mode(TOKEN1); // error 177</pre>
+	 */
+	CONSTANT_VALUE_IS_NOT_A_RECOGNIZED_CHANNEL_NAME(177, "<arg> is not a recognized channel name", ErrorSeverity.ERROR),
 
 	/*
 	 * Backward incompatibility errors