diff --git a/src/drafting/Double/format.ts b/src/drafting/Double/format.ts
index 73bab7f..fccd869 100644
--- a/src/drafting/Double/format.ts
+++ b/src/drafting/Double/format.ts
@@ -47,11 +47,15 @@ export function draftDoubleFormat(value:number,format:NumberDraftFormat) : strin
                 res += sep2 + d;
             }
             let i = vs.substring(0,vs.length - (len === 0 ? 0 : len+1));
+            // Group the digits only. Leaving the minus sign in place would let it
+            // be counted as a digit, so -123 would be grouped as -,123.
+            const sign = i.startsWith('-') ? '-' : '';
+            i = i.substring(sign.length);
             while (i.length > 3) {
                 res = sep1 + i.substring(i.length - 3) + res;
                 i = i.substring(0, i.length - 3);
             }
-            return i + res;
+            return sign + i + res;
         });
     }
 }
\ No newline at end of file
diff --git a/src/drafting/Integer/format.ts b/src/drafting/Integer/format.ts
index 085359c..d98730b 100644
--- a/src/drafting/Integer/format.ts
+++ b/src/drafting/Integer/format.ts
@@ -40,11 +40,15 @@ export function draftIntegerFormat(value:number,format:NumberDraftFormat) : stri
             const vs = value.toFixed(0);
             let res = '';
             let i = vs.substring(0,vs.length);
+            // Group the digits only. Leaving the minus sign in place would let it
+            // be counted as a digit, so -123 would be grouped as -,123.
+            const sign = i.startsWith('-') ? '-' : '';
+            i = i.substring(sign.length);
             while (i.length > 3) {
                 res = sep1 + i.substring(i.length - 3) + res;
                 i = i.substring(0, i.length - 3);
             }
-            return i + res;
+            return sign + i + res;
         });
     }
 }
\ No newline at end of file
diff --git a/test/DraftFormat.test.ts b/test/DraftFormat.test.ts
index 717fe05..5166d2e 100644
--- a/test/DraftFormat.test.ts
+++ b/test/DraftFormat.test.ts
@@ -21,6 +21,27 @@ describe('number format', ()=>{
         expect(drafter(123, TextNumberDraftFormat)).toBe('One Hundred Twenty Three');
         expect(drafter(123456, TextNumberDraftFormat)).toBe('One Lakh Twenty Three Thousand Four Hundred Fifty Six');
     });
+    test('should group a negative integer without a separator after the sign', ()=>{
+        const drafter:any=getDrafter('Integer');
+        expect(drafter(-123, '0,0')).toBe('-123');
+        expect(drafter(-999, '0,0')).toBe('-999');
+        expect(drafter(-123456, '0,0')).toBe('-123,456');
+        expect(drafter(-1234, '0,0')).toBe('-1,234');
+    });
+    test('should group a negative long without a separator after the sign', ()=>{
+        const drafter:any=getDrafter('Long');
+        expect(drafter(-123456, '0,0')).toBe('-123,456');
+    });
+    test('should group a negative double without a separator after the sign', ()=>{
+        const drafter:any=getDrafter('Double');
+        expect(drafter(-123, '0,0.00')).toBe('-123.00');
+        expect(drafter(-123456.78, '0,0.00')).toBe('-123,456.78');
+        expect(drafter(-1234.5, '0,0.00')).toBe('-1,234.50');
+    });
+    test('should still group positive numbers', ()=>{
+        expect((getDrafter('Integer') as any)(123456, '0,0')).toBe('123,456');
+        expect((getDrafter('Double') as any)(123456.78, '0,0.00')).toBe('123,456.78');
+    });
     test('should format double to words', ()=>{
         const drafter:any=getDrafter('Double');
         expect(drafter(123.045, TextNumberDraftFormat)).toBe('One Hundred Twenty Three Point Zero Four Five');