diff --git a/src/libraries/System.Private.CoreLib/src/System/SpanHelpers.ByteMemOps.cs b/src/libraries/System.Private.CoreLib/src/System/SpanHelpers.ByteMemOps.cs
index d54a369eb18c34..600a76e4b3f789 100644
--- a/src/libraries/System.Private.CoreLib/src/System/SpanHelpers.ByteMemOps.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/SpanHelpers.ByteMemOps.cs
@@ -256,7 +256,7 @@ private static unsafe void MemmoveNative(ref byte dest, ref byte src, nuint len)
 
 #if MONO
         [MethodImpl(MethodImplOptions.InternalCall)]
-        private static unsafe extern void memmove(void* dest, void* src, nuint len);
+        private static extern unsafe void memmove(void* dest, void* src, nuint len);
 #else
 #pragma warning disable CS3016 // Arrays as attribute arguments is not CLS-compliant
         [LibraryImport(RuntimeHelpers.QCall, EntryPoint = "memmove")]
@@ -479,7 +479,7 @@ private static unsafe void ZeroMemoryNative(ref byte b, nuint byteLength)
 
 #if MONO
         [MethodImpl(MethodImplOptions.InternalCall)]
-        private static unsafe extern void memset(void* dest, int value, nuint len);
+        private static extern unsafe void memset(void* dest, int value, nuint len);
 #else
 #pragma warning disable CS3016 // Arrays as attribute arguments is not CLS-compliant
         [LibraryImport(RuntimeHelpers.QCall, EntryPoint = "memset")]