diff --git a/src/main/java/jenkins/plugins/git/GitSCMFileSystem.java b/src/main/java/jenkins/plugins/git/GitSCMFileSystem.java
index d419b6e6b1..f9535e372b 100644
--- a/src/main/java/jenkins/plugins/git/GitSCMFileSystem.java
+++ b/src/main/java/jenkins/plugins/git/GitSCMFileSystem.java
@@ -35,6 +35,7 @@
 import hudson.EnvVars;
 import hudson.Extension;
 import hudson.model.Item;
+import hudson.model.Run;
 import hudson.model.TaskListener;
 import hudson.plugins.git.BranchSpec;
 import hudson.plugins.git.GitException;
@@ -284,9 +285,54 @@ public boolean supportsDescriptor(SCMSourceDescriptor descriptor) {
             return AbstractGitSCMSource.class.isAssignableFrom(descriptor.clazz);
         }
 
+        static class HeadNameResult {
+            final String headName;
+            final String prefix;
+
+            private HeadNameResult(String headName, String prefix) {
+                this.headName = headName;
+                this.prefix = prefix;
+            }
+
+            static HeadNameResult calculate(@NonNull BranchSpec branchSpec,
+                                            @CheckForNull SCMRevision rev,
+                                            @CheckForNull EnvVars env) {
+                String branchSpecExpandedName = branchSpec.getName();
+                if (env != null) {
+                    branchSpecExpandedName = env.expand(branchSpecExpandedName);
+                }
+
+                String prefix = Constants.R_HEADS;
+                if (branchSpecExpandedName.startsWith(Constants.R_TAGS)) {
+                    prefix = Constants.R_TAGS;
+                }
+
+                String headName;
+                if (rev != null) {
+                    headName = env.expand(rev.getHead().getName());
+                } else {
+                    if (branchSpecExpandedName.startsWith(prefix)) {
+                        headName = branchSpecExpandedName.substring(prefix.length());
+                    } else if (branchSpecExpandedName.startsWith("*/")) {
+                        headName = branchSpecExpandedName.substring(2);
+                    } else {
+                        headName = branchSpecExpandedName;
+                    }
+                }
+                return new HeadNameResult(headName, prefix);
+            }
+        }
+
         @Override
         public SCMFileSystem build(@NonNull Item owner, @NonNull SCM scm, @CheckForNull SCMRevision rev)
                 throws IOException, InterruptedException {
+            return build(owner, scm, rev, null);
+        }
+
+        @Override
+        public SCMFileSystem build(@NonNull Item owner, @NonNull SCM scm, @CheckForNull SCMRevision rev,
+                                   @CheckForNull Run<?,?> _build)
+                throws IOException, InterruptedException {
             if (rev != null && !(rev instanceof AbstractGitSCMSource.SCMRevisionImpl)) {
                 return null;
             }
@@ -302,6 +348,12 @@ public SCMFileSystem build(@NonNull Item owner, @NonNull SCM scm, @CheckForNull
                 listener.getLogger().println("Git remote url is null");
                 return null;
             }
+
+            EnvVars env = null;
+            if (_build != null) {
+                env = _build.getEnvironment(listener);
+            }
+
             String cacheEntry = AbstractGitSCMSource.getCacheEntry(remote);
             Lock cacheLock = AbstractGitSCMSource.getCacheLock(cacheEntry);
             cacheLock.lock();
@@ -346,27 +398,15 @@ public SCMFileSystem build(@NonNull Item owner, @NonNull SCM scm, @CheckForNull
                 } catch (URISyntaxException ex) {
                     listener.getLogger().println("URI syntax exception for '" + remoteName + "' " + ex);
                 }
-                String prefix = Constants.R_HEADS; 
-                if(branchSpec.getName().startsWith(Constants.R_TAGS)){
-                    prefix = Constants.R_TAGS; 
-                }
-                String headName;
-                if (rev != null) {
-                    headName = rev.getHead().getName();
-                } else {
-                    if (branchSpec.getName().startsWith(prefix)){
-                        headName = branchSpec.getName().substring(prefix.length()); 
-                    } else if (branchSpec.getName().startsWith("*/")) {
-                        headName = branchSpec.getName().substring(2);
-                    } else {
-                        headName = branchSpec.getName();
-                    }
-                }
+
+                HeadNameResult headNameResult = HeadNameResult.calculate(branchSpec, rev, env);
+
                 client.fetch_().prune(true).from(remoteURI, Collections.singletonList(new RefSpec(
-                        "+" + prefix + headName + ":" + Constants.R_REMOTES + remoteName + "/"
-                                + headName))).execute();
+                        "+" + headNameResult.prefix + headNameResult.headName + ":" + Constants.R_REMOTES + remoteName + "/"
+                                + headNameResult.headName))).execute();
+
                 listener.getLogger().println("Done.");
-                return new GitSCMFileSystem(client, remote, Constants.R_REMOTES + remoteName + "/" +headName, (AbstractGitSCMSource.SCMRevisionImpl) rev);
+                return new GitSCMFileSystem(client, remote, Constants.R_REMOTES + remoteName + "/" + headNameResult.headName, (AbstractGitSCMSource.SCMRevisionImpl) rev);
             } finally {
                 cacheLock.unlock();
             }
diff --git a/src/test/java/jenkins/plugins/git/GitSCMFileSystemTest.java b/src/test/java/jenkins/plugins/git/GitSCMFileSystemTest.java
index 9575124853..59b2bf2875 100644
--- a/src/test/java/jenkins/plugins/git/GitSCMFileSystemTest.java
+++ b/src/test/java/jenkins/plugins/git/GitSCMFileSystemTest.java
@@ -42,6 +42,8 @@
 import jenkins.scm.api.SCMRevision;
 import jenkins.scm.api.SCMSource;
 import jenkins.scm.api.SCMSourceDescriptor;
+
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.jenkinsci.plugins.gitclient.Git;
 import org.jenkinsci.plugins.gitclient.GitClient;
@@ -426,6 +428,40 @@ public void filesystem_supports_descriptor() throws Exception {
         assertTrue(SCMFileSystem.supports(descriptor));
     }
 
+    @Issue("JENKINS-42971")
+    @Test
+    public void calculate_head_name_with_env() throws Exception {
+        GitSCMFileSystem.BuilderImpl.HeadNameResult result1 = GitSCMFileSystem.BuilderImpl.HeadNameResult.calculate(new BranchSpec("${BRANCH}"), null,
+                new EnvVars("BRANCH", "master-a"));
+        assertEquals("master-a", result1.headName);
+        assertEquals(Constants.R_HEADS, result1.prefix);
+
+        GitSCMFileSystem.BuilderImpl.HeadNameResult result2 = GitSCMFileSystem.BuilderImpl.HeadNameResult.calculate(new BranchSpec("${BRANCH}"), null,
+                new EnvVars("BRANCH", "refs/heads/master-b"));
+        assertEquals("master-b", result2.headName);
+        assertEquals(Constants.R_HEADS, result2.prefix);
+
+        GitSCMFileSystem.BuilderImpl.HeadNameResult result3 = GitSCMFileSystem.BuilderImpl.HeadNameResult.calculate(new BranchSpec("refs/heads/${BRANCH}"), null,
+                new EnvVars("BRANCH", "master-c"));
+        assertEquals("master-c", result3.headName);
+        assertEquals(Constants.R_HEADS, result3.prefix);
+
+        GitSCMFileSystem.BuilderImpl.HeadNameResult result4 = GitSCMFileSystem.BuilderImpl.HeadNameResult.calculate(new BranchSpec("${BRANCH}"), null,
+                null);
+        assertEquals("${BRANCH}", result4.headName);
+        assertEquals(Constants.R_HEADS, result4.prefix);
+
+        GitSCMFileSystem.BuilderImpl.HeadNameResult result5 = GitSCMFileSystem.BuilderImpl.HeadNameResult.calculate(new BranchSpec("*/${BRANCH}"), null,
+                new EnvVars("BRANCH", "master-d"));
+        assertEquals("master-d", result5.headName);
+        assertEquals(Constants.R_HEADS, result5.prefix);
+
+        GitSCMFileSystem.BuilderImpl.HeadNameResult result6 = GitSCMFileSystem.BuilderImpl.HeadNameResult.calculate(new BranchSpec("*/master-e"), null,
+                new EnvVars("BRANCH", "dummy"));
+        assertEquals("master-e", result6.headName);
+        assertEquals(Constants.R_HEADS, result6.prefix);
+    }
+
     /** inline ${@link hudson.Functions#isWindows()} to prevent a transient remote classloader issue */
     private boolean isWindows() {
         return java.io.File.pathSeparatorChar==';';