diff --git a/src/main/java/org/jenkinsci/plugins/workflow/steps/EnvStep.java b/src/main/java/org/jenkinsci/plugins/workflow/steps/EnvStep.java
index da6de349..f8c55cc7 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/steps/EnvStep.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/steps/EnvStep.java
@@ -49,12 +49,19 @@ public class EnvStep extends Step {
 
     @DataBoundConstructor
     public EnvStep(List<String> overrides) {
-        for (String pair : overrides) {
-            if (pair.indexOf('=') == -1) {
-                throw new IllegalArgumentException(pair);
+        if (overrides == null) {
+            this.overrides = Collections.emptyList();
+        } else {
+            List<String> stored = new ArrayList<>();
+            for (String pair : overrides) {
+                if (pair == null || pair.indexOf('=') == -1) {
+                    throw new IllegalArgumentException(String.valueOf(pair));
+                }
+                // store a trimmed form to normalize whitespace (keys/values are trimmed later too)
+                stored.add(pair.trim());
             }
+            this.overrides = stored;
         }
-        this.overrides = new ArrayList<>(overrides);
     }
 
     public List<String> getOverrides() {
@@ -75,7 +82,7 @@ public static class Execution extends AbstractStepExecutionImpl {
 
         Execution(List<String> overrides, StepContext context) {
             super(context);
-            this.overrides = overrides;
+            this.overrides = overrides == null ? Collections.emptyList() : overrides;
         }
 
         @Override
@@ -83,8 +90,14 @@ public boolean start() throws Exception {
             Map<String, String> overridesM = new HashMap<>();
             for (String pair : overrides) {
                 int split = pair.indexOf('=');
-                assert split != -1;
-                overridesM.put(pair.substring(0, split), pair.substring(split + 1));
+                if (split == -1) {
+                    // defensive: in case an instance is deserialized from an older form
+                    throw new IllegalStateException("Invalid environment override: " + pair);
+                }
+                // trim both key and value to be tolerant of user input like "FOO = bar "
+                String key = pair.substring(0, split).trim();
+                String value = pair.substring(split + 1).trim();
+                overridesM.put(key, value);
             }
             getContext()
                     .newBodyInvoker()
@@ -135,7 +148,7 @@ public boolean takesImplicitBlockArgument() {
         public Step newInstance(StaplerRequest2 req, JSONObject formData) throws FormException {
             String overridesS = formData.getString("overrides");
             List<String> overrides = new ArrayList<>();
-            for (String line : overridesS.split("\r?\n")) {
+            for (String line : overridesS.split("\\r?\\n")) {
                 line = line.trim();
                 if (!line.isEmpty()) {
                     overrides.add(line);
diff --git a/src/test/java/org/jenkinsci/plugins/workflow/steps/EnvStepUnitTest.java b/src/test/java/org/jenkinsci/plugins/workflow/steps/EnvStepUnitTest.java
new file mode 100644
index 00000000..97c1e0c4
--- /dev/null
+++ b/src/test/java/org/jenkinsci/plugins/workflow/steps/EnvStepUnitTest.java
@@ -0,0 +1,29 @@
+package org.jenkinsci.plugins.workflow.steps;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Arrays;
+import org.junit.jupiter.api.Test;
+
+public class EnvStepUnitTest {
+
+    @Test
+    void constructorAcceptsNull() {
+        EnvStep s = new EnvStep(null);
+        assertTrue(s.getOverrides().isEmpty());
+    }
+
+    @Test
+    void constructorRejectsMalformedEntry() {
+        assertThrows(IllegalArgumentException.class, () -> new EnvStep(Arrays.asList("BADPAIR")));
+    }
+
+    @Test
+    void constructorTrimsStoredPair() {
+        EnvStep s = new EnvStep(Arrays.asList("FOO = bar "));
+        assertEquals(1, s.getOverrides().size());
+        assertEquals("FOO = bar", s.getOverrides().get(0));
+    }
+}