diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/DefaultInterpolatedStringHandler.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/DefaultInterpolatedStringHandler.cs
index 0fa80dc2600e48..b945a6b3f8241c 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/DefaultInterpolatedStringHandler.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/DefaultInterpolatedStringHandler.cs
@@ -276,10 +276,10 @@ public void AppendFormatted<T>(T value)
                     return;
                 }
 
-                if (value is ISpanFormattable)
+                if (value is ISpanFormattable spanFormattableValue)
                 {
                     int charsWritten;
-                    while (!((ISpanFormattable)value).TryFormat(_chars.Slice(_pos), out charsWritten, default, _provider)) // constrained call avoiding boxing for value types
+                    while (!spanFormattableValue.TryFormat(_chars.Slice(_pos), out charsWritten, default, _provider))
                     {
                         Grow();
                     }
@@ -343,10 +343,10 @@ public void AppendFormatted<T>(T value, string? format)
                     return;
                 }
 
-                if (value is ISpanFormattable)
+                if (value is ISpanFormattable spanFormattableValue)
                 {
                     int charsWritten;
-                    while (!((ISpanFormattable)value).TryFormat(_chars.Slice(_pos), out charsWritten, format, _provider)) // constrained call avoiding boxing for value types
+                    while (!spanFormattableValue.TryFormat(_chars.Slice(_pos), out charsWritten, format, _provider))
                     {
                         Grow();
                     }