diff --git a/src/lib/parser.ts b/src/lib/parser.ts
index 29db4f5..528600a 100644
--- a/src/lib/parser.ts
+++ b/src/lib/parser.ts
@@ -50,7 +50,7 @@ export class Parser {
     const split = this.parent.alias.split(match);
     const check =
       split && hasAssigned
-        ? this.checkArgsList(match, split.argsList)
+        ? this.checkArgsList(split.argsList)
         : { assign: !!split, options: null };
     if (split && check.assign) {
       // treat left over from split as argument
@@ -65,17 +65,19 @@ export class Parser {
     }
   }
 
-  private checkArgsList(arg: string, argsList: [string, ...string[]][]) {
+  private checkArgsList(argsList: [string, ...string[]][]) {
     // e.g. -fb=value, cases:
     // -b is null -> error
     // -b is not assignable -> treat as value
     // -b is assignable -> continue split
-    const options =
-      argsList.length > 0
-        ? this.parent.parse(argsList[argsList.length - 1][0])
-        : null;
+    const arg = argsList.length > 0 ? argsList[argsList.length - 1][0] : null;
+    const hasArg = arg != null;
+    const options = hasArg ? this.parent.parse(arg) : null;
     // allow assign if no options or if assignable
-    return { options, assign: !options || isAssignable(arg, options) };
+    return {
+      options,
+      assign: !options || (hasArg && isAssignable(arg, options))
+    };
   }
 
   private saveArg(arg: string, assigned?: string) {
@@ -95,7 +97,7 @@ export class Parser {
     const aliasArgs = this.parent.alias.getArgs(arg);
     const check =
       aliasArgs && hasAssigned
-        ? this.checkArgsList(arg, aliasArgs)
+        ? this.checkArgsList(aliasArgs)
         : { assign: !!aliasArgs, options: null };
     const save = aliasArgs && check.assign;
     if (save) {
diff --git a/test/argstree.spec.ts b/test/argstree.spec.ts
index dae72aa..045274b 100644
--- a/test/argstree.spec.ts
+++ b/test/argstree.spec.ts
@@ -669,6 +669,37 @@ describe('argstree', () => {
     expect(node.children[0].args).to.deep.equal(['foo', 'bar']);
   });
 
+  it('should handle `assign` option when parsing `=` for aliases', () => {
+    const node = argstree(
+      ['-f=0', 'f=0', '-b=0', 'b=0', '-f2=0', 'f2=0', '-b2=0', 'b2=0'],
+      {
+        alias: {
+          '-f': '--foo',
+          f: '--foo',
+          '-b': '--bar',
+          b: '--bar',
+          '-f2': 'foo',
+          f2: 'foo',
+          '-b2': 'bar',
+          b2: 'bar'
+        },
+        args: {
+          '--foo': { maxRead: 0 },
+          '--bar': { maxRead: 0, assign: false },
+          foo: { maxRead: 0 },
+          bar: { maxRead: 0, assign: true }
+        }
+      }
+    );
+    expect(node.args).to.deep.equal(['-b=0', 'b=0', '-f2=0', 'f2=0']);
+    expect(node.children).to.have.length(4);
+    const match = ['--foo', '--foo', 'bar', 'bar'];
+    node.children.forEach((child, index) => {
+      expect(child.id).to.equal(match[index]);
+      expect(child.args).to.deep.equal(['0']);
+    });
+  });
+
   it('should not parse `=` for combined aliases if last option is not assignable', () => {
     // force empty arrays
     const options = {
diff --git a/test/stringify.spec.ts b/test/stringify.spec.ts
index 8e3002f..e496d17 100644
--- a/test/stringify.spec.ts
+++ b/test/stringify.spec.ts
@@ -162,7 +162,7 @@ describe('stringify', () => {
         args: {
           foo: {},
           bar: {},
-          baz: { args: { test: { max: 0 }, '--': {} } }
+          baz: { assign: true, args: { test: { max: 0 }, '--': {} } }
         }
       }
     );