diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3e855f19..ec09e7ae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -38,6 +38,8 @@
 
 * Fixed optimizations removing pointless stores to local variables.
 
+* Fixed name clashes when passing parameters to functions.
+
 * Fixed `#use` not accessing all preprocessor parameters.
 
 * Fixed `#pragma` not respecting `#if`.
diff --git a/src/main/scala/millfork/compiler/AbstractExpressionCompiler.scala b/src/main/scala/millfork/compiler/AbstractExpressionCompiler.scala
index 5f22e976..f9f0554d 100644
--- a/src/main/scala/millfork/compiler/AbstractExpressionCompiler.scala
+++ b/src/main/scala/millfork/compiler/AbstractExpressionCompiler.scala
@@ -29,7 +29,7 @@ class AbstractExpressionCompiler[T <: AbstractCode] {
 
   def callingContext(ctx: CompilationContext, callee: String, v: VariableInMemory): CompilationContext = {
     val result = new Environment(Some(ctx.env), "", ctx.options.platform.cpuFamily, ctx.options)
-    val localName = v.name.stripPrefix(callee + '$')
+    val localName = v.name + "`aa"
     result.addVariable(ctx.options, localName, v, None)
     ctx.copy(env = result)
   }
diff --git a/src/main/scala/millfork/compiler/mos/MosExpressionCompiler.scala b/src/main/scala/millfork/compiler/mos/MosExpressionCompiler.scala
index 0f6601ab..f46ff6a9 100644
--- a/src/main/scala/millfork/compiler/mos/MosExpressionCompiler.scala
+++ b/src/main/scala/millfork/compiler/mos/MosExpressionCompiler.scala
@@ -1404,7 +1404,7 @@ object MosExpressionCompiler extends AbstractExpressionCompiler[AssemblyLine] {
                     params.zip(paramVars).flatMap {
                       case (paramExpr, paramVar) =>
                         val callCtx = callingContext(ctx, function.name, paramVar)
-                        compileAssignment(callCtx, paramExpr, VariableExpression(paramVar.name))
+                        compileAssignment(callCtx, paramExpr, VariableExpression(paramVar.name + "`aa"))
                     } ++ List(AssemblyLine.absoluteOrLongAbsolute(JSR, function, ctx.options))
                 }
                 result
diff --git a/src/main/scala/millfork/compiler/z80/Z80ExpressionCompiler.scala b/src/main/scala/millfork/compiler/z80/Z80ExpressionCompiler.scala
index ecf1fd00..3d4b665d 100644
--- a/src/main/scala/millfork/compiler/z80/Z80ExpressionCompiler.scala
+++ b/src/main/scala/millfork/compiler/z80/Z80ExpressionCompiler.scala
@@ -975,11 +975,11 @@ object Z80ExpressionCompiler extends AbstractExpressionCompiler[ZLine] {
                             val callCtx = callingContext(ctx, function.name, paramVar)
                             paramVar.typ.size match {
                               case 1 =>
-                                compileToA(ctx, paramExpr) ++ storeA(callCtx, VariableExpression(paramVar.name), paramVar.typ.isSigned)
+                                compileToA(ctx, paramExpr) ++ storeA(callCtx, VariableExpression(paramVar.name + "`aa"), paramVar.typ.isSigned)
                               case 2 =>
-                                compileToHL(ctx, paramExpr) ++ storeHL(callCtx, VariableExpression(paramVar.name), paramVar.typ.isSigned)
+                                compileToHL(ctx, paramExpr) ++ storeHL(callCtx, VariableExpression(paramVar.name + "`aa"), paramVar.typ.isSigned)
                               case _ =>
-                                storeLarge(callCtx, VariableExpression(paramVar.name), paramExpr)
+                                storeLarge(callCtx, VariableExpression(paramVar.name + "`aa"), paramExpr)
                             }
                         } ++ List(ZLine(CALL, NoRegisters, function.toAddress))
                     }
diff --git a/src/main/scala/millfork/env/Environment.scala b/src/main/scala/millfork/env/Environment.scala
index e95e3c16..9c9e410a 100644
--- a/src/main/scala/millfork/env/Environment.scala
+++ b/src/main/scala/millfork/env/Environment.scala
@@ -214,6 +214,12 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
     }
   }
 
+  private def addThing(localName: String, t: Thing, position: Option[Position]): Unit = {
+    if (assertNotDefined(t.name, position)) {
+      things(localName) = t
+    }
+  }
+
   def getReturnedVariables(statements: Seq[Statement]): Set[String] = {
     statements.flatMap {
       case ReturnStatement(Some(VariableExpression(v))) => Set(v)
@@ -1499,19 +1505,19 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
   def addVariable(options: CompilationOptions, localName: String, variable: Variable, position: Option[Position]): Unit = {
     variable match {
       case v: StackVariable =>
-        addThing(v, position)
+        addThing(localName, v, position)
         for ((suffix, offset, t) <- getSubvariables(v.typ)) {
           addThing(StackVariable(prefix + localName + suffix, t, baseStackOffset + offset), position)
         }
       case v: MemoryVariable =>
-        addThing(v, position)
+        addThing(localName, v, position)
         for ((suffix, offset, t) <- getSubvariables(v.typ)) {
           val subv = RelativeVariable(prefix + localName + suffix, v.toAddress + offset, t, zeropage = v.zeropage, declaredBank = v.declaredBank, isVolatile = v.isVolatile)
           addThing(subv, position)
           registerAddressConstant(subv, position, options, Some(t))
         }
       case v: VariableInMemory =>
-        addThing(v, position)
+        addThing(localName, v, position)
         addThing(ConstantThing(v.name + "`", v.toAddress, get[Type]("word")), position)
         for ((suffix, offset, t) <- getSubvariables(v.typ)) {
           val subv = RelativeVariable(prefix + localName + suffix, v.toAddress + offset, t, zeropage = v.zeropage, declaredBank = v.declaredBank, isVolatile = v.isVolatile)