diff --git a/src/libraries/System.Private.CoreLib/src/System/String.cs b/src/libraries/System.Private.CoreLib/src/System/String.cs
index 7ca88a4b29c79..76048da7b75c2 100644
--- a/src/libraries/System.Private.CoreLib/src/System/String.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/String.cs
@@ -321,35 +321,9 @@ string Ctor(char c, int count)
             }
 
             string result = FastAllocateString(count);
-
-            if (c != '\0') // Fast path null char string
+            if (c != '\0')
             {
-                unsafe
-                {
-                    fixed (char* dest = &result._firstChar)
-                    {
-                        uint cc = (uint)((c << 16) | c);
-                        uint* dmem = (uint*)dest;
-                        if (count >= 4)
-                        {
-                            count -= 4;
-                            do
-                            {
-                                dmem[0] = cc;
-                                dmem[1] = cc;
-                                dmem += 2;
-                                count -= 4;
-                            } while (count >= 0);
-                        }
-                        if ((count & 2) != 0)
-                        {
-                            *dmem = cc;
-                            dmem++;
-                        }
-                        if ((count & 1) != 0)
-                            ((char*)dmem)[0] = c;
-                    }
-                }
+                SpanHelpers.Fill(ref result._firstChar, (uint)count, c);
             }
             return result;
         }