diff --git a/native-image-support/src/main/java/com/google/cloud/nativeimage/features/substitutions/ApiClientVersionSubstitutions.java b/native-image-support/src/main/java/com/google/cloud/nativeimage/features/substitutions/ApiClientVersionSubstitutions.java
deleted file mode 100644
index ccff1010..00000000
--- a/native-image-support/src/main/java/com/google/cloud/nativeimage/features/substitutions/ApiClientVersionSubstitutions.java
+++ /dev/null
@@ -1,68 +0,0 @@
-/*
- * Copyright 2020-2021 Google LLC
- *
- * 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
- *
- *     https://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.cloud.nativeimage.features.substitutions;
-
-import com.oracle.svm.core.annotate.Alias;
-import com.oracle.svm.core.annotate.Substitute;
-import com.oracle.svm.core.annotate.TargetClass;
-import java.util.function.BooleanSupplier;
-
-/**
- * Substitution for setting Java version correctly in the Google Java Http Client.
- */
-@TargetClass(
-    className =
-        "com.google.api.client.googleapis.services.AbstractGoogleClientRequest$ApiClientVersion",
-    onlyWith = ApiClientVersionSubstitutions.OnlyIfInClassPath.class)
-final class ApiClientVersionSubstitutions {
-
-  @Alias
-  private String versionString;
-
-  @Substitute
-  public String toString() {
-    String[] tokens = versionString.split(" ");
-
-    if (tokens.length > 0 && tokens[0].startsWith("gl-java")) {
-      tokens[0] += "-graalvm";
-      return String.join(" ", tokens);
-    } else {
-      return versionString;
-    }
-  }
-
-  private ApiClientVersionSubstitutions() {
-  }
-
-  static class OnlyIfInClassPath implements BooleanSupplier {
-
-    @Override
-    public boolean getAsBoolean() {
-      try {
-        // Note: Set initialize = false to avoid initializing the class when looking it up.
-        Class.forName(
-            "com.google.api.client.googleapis.services."
-                + "AbstractGoogleClientRequest$ApiClientVersion",
-            false,
-            Thread.currentThread().getContextClassLoader());
-        return true;
-      } catch (ClassNotFoundException e) {
-        return false;
-      }
-    }
-  }
-}
diff --git a/native-image-support/src/main/java/com/google/cloud/nativeimage/features/substitutions/GaxPropertiesSubstitutions.java b/native-image-support/src/main/java/com/google/cloud/nativeimage/features/substitutions/GaxPropertiesSubstitutions.java
deleted file mode 100644
index 70d5ddaf..00000000
--- a/native-image-support/src/main/java/com/google/cloud/nativeimage/features/substitutions/GaxPropertiesSubstitutions.java
+++ /dev/null
@@ -1,58 +0,0 @@
-/*
- * Copyright 2020-2021 Google LLC
- *
- * 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
- *
- *     https://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.cloud.nativeimage.features.substitutions;
-
-import com.oracle.svm.core.annotate.Alias;
-import com.oracle.svm.core.annotate.RecomputeFieldValue;
-import com.oracle.svm.core.annotate.RecomputeFieldValue.Kind;
-import com.oracle.svm.core.annotate.TargetClass;
-import java.util.function.BooleanSupplier;
-
-/**
- * This file contains the GaxProperties substitution to correctly set the Java language string
- * in API call headers for Native Image users.
- */
-@TargetClass(
-    className = "com.google.api.gax.core.GaxProperties",
-    onlyWith = GaxPropertiesSubstitutions.OnlyIfInClassPath.class)
-final class GaxPropertiesSubstitutions {
-
-  @Alias
-  @RecomputeFieldValue(kind = Kind.FromAlias)
-  private static String JAVA_VERSION = System.getProperty("java.version") + "-graalvm";
-
-  private GaxPropertiesSubstitutions() {
-  }
-
-  static class OnlyIfInClassPath implements BooleanSupplier {
-
-    @Override
-    public boolean getAsBoolean() {
-      try {
-        // Note: Set initialize = false to avoid initializing the class when looking it up.
-        Class.forName(
-            "com.google.api.gax.core.GaxProperties",
-            false,
-            Thread.currentThread().getContextClassLoader());
-        return true;
-      } catch (ClassNotFoundException e) {
-        return false;
-      }
-    }
-  }
-}
-