diff --git a/lib/yargs-parser.ts b/lib/yargs-parser.ts
index 48a2d0f2..ac1954b6 100644
--- a/lib/yargs-parser.ts
+++ b/lib/yargs-parser.ts
@@ -626,7 +626,8 @@ export class YargsParser {
 
       // increment a count given as arg (either no value or value parsed as boolean)
       if (checkAllAliases(key, flags.counts) && (isUndefined(value) || typeof value === 'boolean')) {
-        value = increment()
+        // COUNT_INCREMENT is a unique sentinel, not the number 1.
+        value = COUNT_INCREMENT as unknown as typeof value
       }
 
       // Set normalized value when key is in 'normalize' and in 'arrays'
@@ -850,7 +851,7 @@ export class YargsParser {
         }
       }
 
-      if (value === increment()) {
+      if (value === COUNT_INCREMENT) {
         o[key] = increment(o[key])
       } else if (Array.isArray(o[key])) {
         if (duplicate && isTypeArray && isValueArray) {
@@ -1098,6 +1099,11 @@ function combineAliases (aliases: Dictionary<string | string[]>): Dictionary<str
   return combined
 }
 
+// Sentinel so a real option value of 1 is not treated as a count step.
+// processValue used to assign increment(), which returns 1, and setKey
+// compared value === increment(), so `-x 3 -x 1` became 4 instead of [3, 1].
+const COUNT_INCREMENT = Symbol('yargs-parser-count-increment')
+
 // this function should only be called when a count is given as an arg
 // it is NOT called to set a default value
 // thus we can start the count at 1 instead of 0
diff --git a/test/yargs-parser.mjs b/test/yargs-parser.mjs
index 4c692375..44ed0384 100644
--- a/test/yargs-parser.mjs
+++ b/test/yargs-parser.mjs
@@ -1666,6 +1666,16 @@ describe('yargs-parser', function () {
       parse.should.have.property('v').and.deep.equal(['a', 'b', 'c'])
       parse.should.have.property('_').with.length(0)
     })
+    it('should not treat a later value of 1 as a count increment (#506)', function () {
+      const parse = parser(['-x', '3', '-x', '1'])
+      parse.should.have.property('x').and.deep.equal([3, 1])
+      parse.should.have.property('_').with.length(0)
+    })
+    it('should keep a later value of 1 when duplicate-arguments-array is false (#506)', function () {
+      const parse = parser(['-x', '3', '-x', '1'], { configuration: { 'duplicate-arguments-array': false } })
+      parse.should.have.property('x').and.equal(1)
+      parse.should.have.property('_').with.length(0)
+    })
     it('should keep only the last value if the same option is specified multiple times (duplicate-arguments-false)', function () {
       const parse = parser(['-v', 'a', '-v', 'b', '-v', 'c'], { configuration: { 'duplicate-arguments-array': false } })
       parse.should.have.property('v').and.equal('c')