diff --git a/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs b/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs
index 55625b412f48eb..ace5eb7d1d0987 100644
--- a/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs
+++ b/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs
@@ -341,7 +341,7 @@ public override void BeginExceptFilterBlock()
             current.MarkFilterAddr(ILOffset);
         }
 
-        public override void BeginCatchBlock(Type exceptionType)
+        public override void BeginCatchBlock(Type? exceptionType)
         {
             if (CurrExcStackCount == 0)
                 throw new NotSupportedException(SR.Argument_NotInExceptionBlock);
diff --git a/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs b/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
index 26c1ae27f88ad8..dfcc66d6dcb699 100644
--- a/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
+++ b/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
@@ -992,7 +992,7 @@ public virtual void BeginExceptFilterBlock()
             current.MarkFilterAddr(m_length);
         }
 
-        public virtual void BeginCatchBlock(Type exceptionType)
+        public virtual void BeginCatchBlock(Type? exceptionType)
         {
             // Begins a catch block.  Emits a branch instruction to the end of the current exception block.
 
diff --git a/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs b/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
index b5e8e0dc0230f9..49190e8c371258 100644
--- a/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
+++ b/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
@@ -21,7 +21,7 @@ public virtual int ILOffset
             }
         }
 
-        public virtual void BeginCatchBlock(Type exceptionType)
+        public virtual void BeginCatchBlock(Type? exceptionType)
         {
         }
 
diff --git a/src/libraries/System.Linq.Expressions/src/System/Linq/Expressions/Compiler/LambdaCompiler.Statements.cs b/src/libraries/System.Linq.Expressions/src/System/Linq/Expressions/Compiler/LambdaCompiler.Statements.cs
index 321a38f8a069eb..f01cff002fc97c 100644
--- a/src/libraries/System.Linq.Expressions/src/System/Linq/Expressions/Compiler/LambdaCompiler.Statements.cs
+++ b/src/libraries/System.Linq.Expressions/src/System/Linq/Expressions/Compiler/LambdaCompiler.Statements.cs
@@ -946,7 +946,7 @@ private void EmitCatchStart(CatchBlock cb)
             // begin the catch, clear the exception, we've
             // already saved it
             _ilg.MarkLabel(endFilter);
-            _ilg.BeginCatchBlock(exceptionType: null!);
+            _ilg.BeginCatchBlock(exceptionType: null);
             _ilg.Emit(OpCodes.Pop);
         }
 
diff --git a/src/libraries/System.Reflection.Emit.ILGeneration/ref/System.Reflection.Emit.ILGeneration.cs b/src/libraries/System.Reflection.Emit.ILGeneration/ref/System.Reflection.Emit.ILGeneration.cs
index 449916fb2a442f..fbcc94202c48b8 100644
--- a/src/libraries/System.Reflection.Emit.ILGeneration/ref/System.Reflection.Emit.ILGeneration.cs
+++ b/src/libraries/System.Reflection.Emit.ILGeneration/ref/System.Reflection.Emit.ILGeneration.cs
@@ -17,7 +17,7 @@ public partial class ILGenerator
     {
         internal ILGenerator() { }
         public virtual int ILOffset { get { throw null; } }
-        public virtual void BeginCatchBlock(System.Type exceptionType) { }
+        public virtual void BeginCatchBlock(System.Type? exceptionType) { }
         public virtual void BeginExceptFilterBlock() { }
         public virtual System.Reflection.Emit.Label BeginExceptionBlock() { throw null; }
         public virtual void BeginFaultBlock() { }
diff --git a/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.Mono.cs b/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.Mono.cs
index 249e596ef1b2ef..c1f4df1d9fab0e 100644
--- a/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.Mono.cs
+++ b/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.Mono.cs
@@ -343,7 +343,7 @@ private void InternalEndClause()
             }
         }
 
-        public virtual void BeginCatchBlock(Type exceptionType)
+        public virtual void BeginCatchBlock(Type? exceptionType)
         {
             if (!InExceptionBlock)
                 throw new NotSupportedException("Not in an exception block");