diff --git a/src/main/java/com/google/common/css/compiler/passes/PassRunner.java b/src/main/java/com/google/common/css/compiler/passes/PassRunner.java
index fcfa37f..ee9dfa6 100644
--- a/src/main/java/com/google/common/css/compiler/passes/PassRunner.java
+++ b/src/main/java/com/google/common/css/compiler/passes/PassRunner.java
@@ -79,7 +79,6 @@ public void runPasses(CssTree cssTree) {
         new CreateComponentNodes(cssTree.getMutatingVisitController(),
                 errorManager).runPass();
         new ValidatePropertyValues(cssTree.getVisitController(), errorManager).runPass();
-        new WarnOnCustomProperty(cssTree.getVisitController(), errorManager).runPass();
 
         new HandleUnknownAtRuleNodes(cssTree.getMutatingVisitController(),
                 errorManager, job.allowedAtRules,
diff --git a/src/main/java/com/google/common/css/compiler/passes/WarnOnCustomProperty.java b/src/main/java/com/google/common/css/compiler/passes/WarnOnCustomProperty.java
deleted file mode 100644
index 69c7ac3..0000000
--- a/src/main/java/com/google/common/css/compiler/passes/WarnOnCustomProperty.java
+++ /dev/null
@@ -1,72 +0,0 @@
-/*
- * Copyright 2017 Google Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.google.common.css.compiler.passes;
-
-import com.google.common.css.compiler.ast.*;
-
-/**
- * A compiler pass that warns when custom properties declarations and references are encountered,
- * since they are not yet supported by all the major browsers.
- */
-public class WarnOnCustomProperty extends DefaultTreeVisitor implements CssCompilerPass {
-
-    private static final String VAR_FUNCTION_NAME = "var";
-
-    static final String DECLARATION_WARNING_MSG = "Custom property declaration encountered. "
-            + "Please note that custom properties do not work with all major browsers, and their use is "
-            + "discouraged.";
-
-    static final String REFERENCE_WARNING_MSG = "Custom property reference encountered. "
-            + "Please note that custom properties do not work with all major browsers, and their use "
-            + "is discouraged.";
-
-    private final ErrorManager errorManager;
-
-    private final VisitController visitController;
-
-    public WarnOnCustomProperty(VisitController visitController, ErrorManager errorManager) {
-        this.visitController = visitController;
-        this.errorManager = errorManager;
-    }
-
-    @Override
-    public boolean enterDeclaration(CssDeclarationNode declaration) {
-        if (declaration.isCustomDeclaration()) {
-            errorManager.reportWarning(
-                    new GssError(
-                            DECLARATION_WARNING_MSG,
-                            declaration.getSourceCodeLocation()));
-        }
-
-        return super.enterDeclaration(declaration);
-    }
-
-    @Override
-    public boolean enterFunctionNode(CssFunctionNode value) {
-        if (value.getFunctionName().equals(VAR_FUNCTION_NAME)) {
-            errorManager.reportWarning(
-                    new GssError(REFERENCE_WARNING_MSG, value.getSourceCodeLocation()));
-        }
-
-        return super.enterFunctionNode(value);
-    }
-
-    @Override
-    public void runPass() {
-        visitController.startVisit(this);
-    }
-}
diff --git a/src/test/java/com/google/common/css/compiler/passes/WarnOnCustomPropertyTest.java b/src/test/java/com/google/common/css/compiler/passes/WarnOnCustomPropertyTest.java
deleted file mode 100644
index ebac21c..0000000
--- a/src/test/java/com/google/common/css/compiler/passes/WarnOnCustomPropertyTest.java
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * Copyright 2017 Google Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.google.common.css.compiler.passes;
-
-import com.google.common.css.compiler.ast.testing.NewFunctionalTestBase;
-import org.junit.jupiter.api.Test;
-
-/**
- * Unit tests for {@link WarnOnCustomProperty}.
- */
-class WarnOnCustomPropertyTest extends NewFunctionalTestBase {
-
-    @Override
-    protected void runPass() {
-        WarnOnCustomProperty pass = new WarnOnCustomProperty(tree.getVisitController(), errorManager);
-        pass.runPass();
-    }
-
-    @Test
-    void testWarnsOnDeclaration() throws Exception {
-        parseAndRun(":root { --test: 123; }", WarnOnCustomProperty.DECLARATION_WARNING_MSG);
-    }
-
-    @Test
-    void testWarnsOnReference() throws Exception {
-        parseAndRun(":root { background: var(--test); }", WarnOnCustomProperty.REFERENCE_WARNING_MSG);
-    }
-}