diff --git a/Content.Tests/DMProject/Broken Tests/Statements/For/reuse_decl_const.dm b/Content.Tests/DMProject/Tests/Statements/For/reuse_decl_const.dm
similarity index 89%
rename from Content.Tests/DMProject/Broken Tests/Statements/For/reuse_decl_const.dm
rename to Content.Tests/DMProject/Tests/Statements/For/reuse_decl_const.dm
index 4b404cb05c..2f39dc4f12 100644
--- a/Content.Tests/DMProject/Broken Tests/Statements/For/reuse_decl_const.dm	
+++ b/Content.Tests/DMProject/Tests/Statements/For/reuse_decl_const.dm
@@ -1,4 +1,4 @@
-// COMPILE ERROR
+// COMPILE ERROR OD0501
 
 /datum
 	var/const/idx = 0
diff --git a/Content.Tests/DMProject/Tests/Statements/For/reuse_decl_const2.dm b/Content.Tests/DMProject/Tests/Statements/For/reuse_decl_const2.dm
new file mode 100644
index 0000000000..a8144a4359
--- /dev/null
+++ b/Content.Tests/DMProject/Tests/Statements/For/reuse_decl_const2.dm
@@ -0,0 +1,18 @@
+// COMPILE ERROR OD0501
+
+/datum
+	var/const/idx = 0
+	var/c = 0
+	proc/do_loop()
+		for (idx in list(1,2,3))
+			c += idx
+
+/proc/RunTest()
+	var/datum/d = new
+	d.do_loop()
+
+	var/const/idx = 0
+	var/c = 0
+	for (idx in list(1,2,3))
+		c += idx
+
diff --git a/DMCompiler/DM/Builders/DMProcBuilder.cs b/DMCompiler/DM/Builders/DMProcBuilder.cs
index e4fcd52a2d..38f2c0d729 100644
--- a/DMCompiler/DM/Builders/DMProcBuilder.cs
+++ b/DMCompiler/DM/Builders/DMProcBuilder.cs
@@ -489,6 +489,10 @@ public void ProcessStatementFor(DMASTProcStatementFor statementFor) {
 
                             var outputVar = _exprBuilder.Create(outputExpr);
 
+                            if (outputVar is Local { LocalVar: DMProc.LocalConstVariable } or Field { IsConst: true }) {
+                                compiler.Emit(WarningCode.WriteToConstant, outputExpr.Location, "Cannot change constant value");
+                            }
+
                             var start = _exprBuilder.Create(exprRange.StartRange);
                             var end = _exprBuilder.Create(exprRange.EndRange);
                             var step = exprRange.Step != null
@@ -520,7 +524,10 @@ public void ProcessStatementFor(DMASTProcStatementFor statementFor) {
 
                             if (outputVar is Local outputLocal) {
                                 outputLocal.LocalVar.ExplicitValueType = statementFor.DMTypes;
-                            }
+                            if(outputLocal.LocalVar is DMProc.LocalConstVariable)
+                                compiler.Emit(WarningCode.WriteToConstant, outputExpr.Location, "Cannot change constant value");
+                            } else if (outputVar is Field { IsConst: true })
+                                compiler.Emit(WarningCode.WriteToConstant, outputExpr.Location, "Cannot change constant value");
 
                             ProcessStatementForList(list, outputVar, statementFor.DMTypes, statementFor.Body);
                             break;
diff --git a/DMCompiler/DM/Expressions/LValue.cs b/DMCompiler/DM/Expressions/LValue.cs
index a32902f4f9..d5fd05f468 100644
--- a/DMCompiler/DM/Expressions/LValue.cs
+++ b/DMCompiler/DM/Expressions/LValue.cs
@@ -122,6 +122,7 @@ public override void EmitPushInitial(ExpressionContext ctx) {
 
 // Identifier of field
 internal sealed class Field(Location location, DMVariable variable, DMComplexValueType valType) : LValue(location, variable.Type) {
+    public bool IsConst { get; } = variable.IsConst;
     public override DMComplexValueType ValType => valType;
 
     public override void EmitPushInitial(ExpressionContext ctx) {