diff --git a/src/libraries/Common/src/System/Text/ValueStringBuilder.cs b/src/libraries/Common/src/System/Text/ValueStringBuilder.cs
index 75814574852a0d..cfbad43bf7b83f 100644
--- a/src/libraries/Common/src/System/Text/ValueStringBuilder.cs
+++ b/src/libraries/Common/src/System/Text/ValueStringBuilder.cs
@@ -198,11 +198,7 @@ public void Append(char c, int count)
                 Grow(count);
             }
 
-            Span<char> dst = _chars.Slice(_pos, count);
-            for (int i = 0; i < dst.Length; i++)
-            {
-                dst[i] = c;
-            }
+            _chars.Slice(_pos, count).Fill(c);
             _pos += count;
         }
 
diff --git a/src/libraries/Common/src/System/Text/ValueStringBuilder_1.cs b/src/libraries/Common/src/System/Text/ValueStringBuilder_1.cs
index 42c0c818be6332..d4e89a2f748680 100644
--- a/src/libraries/Common/src/System/Text/ValueStringBuilder_1.cs
+++ b/src/libraries/Common/src/System/Text/ValueStringBuilder_1.cs
@@ -244,11 +244,7 @@ public void Append(TChar c, int count)
                 Grow(count);
             }
 
-            Span<TChar> dst = _chars.Slice(_pos, count);
-            for (int i = 0; i < dst.Length; i++)
-            {
-                dst[i] = c;
-            }
+            _chars.Slice(_pos, count).Fill(c);
             _pos += count;
         }