diff --git a/src/namedef.h b/src/namedef.h
index a5abfa5a1..3966c95e7 100644
--- a/src/namedef.h
+++ b/src/namedef.h
@@ -732,3 +732,4 @@ xx(__decorate_internal_float__)
 xx(DamageFunction)
 xx(Length)
 xx(Unit)
+xx(A_Jump)
\ No newline at end of file
diff --git a/src/p_actionfunctions.cpp b/src/p_actionfunctions.cpp
index 0e9620564..9f3a088d6 100644
--- a/src/p_actionfunctions.cpp
+++ b/src/p_actionfunctions.cpp
@@ -1148,7 +1148,7 @@ DEFINE_ACTION_FUNCTION(AActor, A_BulletAttack)
 DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_Jump)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_INT_DEF(maxchance);
+	PARAM_INT(maxchance);
 
 	paramnum++;		// Increment paramnum to point at the first jump target
 	int count = numparam - paramnum;
diff --git a/src/p_maputl.cpp b/src/p_maputl.cpp
index 04372f0ed..0a1d831d8 100644
--- a/src/p_maputl.cpp
+++ b/src/p_maputl.cpp
@@ -532,6 +532,17 @@ void AActor::SetOrigin(double x, double y, double z, bool moving)
 	if (!moving) ClearInterpolation();
 }
 
+DEFINE_ACTION_FUNCTION(AActor, SetOrigin)
+{
+	PARAM_SELF_PROLOGUE(AActor);
+	PARAM_FLOAT(x);
+	PARAM_FLOAT(y);
+	PARAM_FLOAT(z);
+	PARAM_BOOL(moving);
+	self->SetOrigin(x, y, z, moving);
+	return 0;
+}
+
 //===========================================================================
 //
 // FBlockNode - allows to link actors into multiple blocks in the blockmap
diff --git a/src/scripting/codegeneration/codegen.cpp b/src/scripting/codegeneration/codegen.cpp
index f8fd03946..d87e601ff 100644
--- a/src/scripting/codegeneration/codegen.cpp
+++ b/src/scripting/codegeneration/codegen.cpp
@@ -334,7 +334,7 @@ PPrototype *FxExpression::ReturnProto()
 //
 //==========================================================================
 
-static void EmitParameter(VMFunctionBuilder *build, FxExpression *operand, const FScriptPosition &pos)
+static int EmitParameter(VMFunctionBuilder *build, FxExpression *operand, const FScriptPosition &pos)
 {
 	ExpEmit where = operand->Emit(build);
 
@@ -342,6 +342,7 @@ static void EmitParameter(VMFunctionBuilder *build, FxExpression *operand, const
 	{
 		pos.Message(MSG_ERROR, "Attempted to pass a non-value");
 		build->Emit(OP_PARAM, 0, where.RegType, where.RegNum);
+		return 1;
 	}
 	else
 	{
@@ -350,8 +351,17 @@ static void EmitParameter(VMFunctionBuilder *build, FxExpression *operand, const
 		{
 			regtype |= REGT_KONST;
 		}
+		else if (where.RegCount == 2)
+		{
+			regtype |= REGT_MULTIREG2;
+		}
+		else if (where.RegCount == 3)
+		{
+			regtype |= REGT_MULTIREG3;
+		}
 		build->Emit(OP_PARAM, 0, regtype, where.RegNum);
 		where.Free(build);
+		return where.RegCount;
 	}
 }
 
@@ -5873,6 +5883,7 @@ FxExpression *FxVMFunctionCall::Resolve(FCompileContext& ctx)
 			delete this;
 			return nullptr;
 		}
+
 		for (unsigned i = 0; i < ArgList->Size(); i++)
 		{
 			// Varargs must all have the same type as the last typed argument. A_Jump is the only function using it.
@@ -5888,6 +5899,18 @@ FxExpression *FxVMFunctionCall::Resolve(FCompileContext& ctx)
 			failed |= (x == nullptr);
 			(*ArgList)[i] = x;
 		}
+		int numargs = ArgList->Size() + implicit;
+		if ((unsigned)numargs < argtypes.Size() && argtypes[numargs] != nullptr)
+		{
+			auto flags = Function->Variants[0].ArgFlags[numargs];
+			if (!(flags & VARF_Optional))
+			{
+				ScriptPosition.Message(MSG_ERROR, "Insufficient arguments in call to %s", Function->SymbolName.GetChars());
+				delete this;
+				return nullptr;
+			}
+		}
+		
 	}
 	if (failed)
 	{
@@ -5917,7 +5940,7 @@ ExpEmit FxVMFunctionCall::Emit(VMFunctionBuilder *build)
 {
 	assert((build->IsActionFunc && build->Registers[REGT_POINTER].GetMostUsed() >= NAP) ||
 		(!build->IsActionFunc && build->Registers[REGT_POINTER].GetMostUsed() >= 1));
-	int count = (ArgList ? ArgList->Size() : 0);
+	int count = 0; (ArgList ? ArgList->Size() : 0);
 
 	if (count == 1)
 	{
@@ -5928,6 +5951,7 @@ ExpEmit FxVMFunctionCall::Emit(VMFunctionBuilder *build)
 		}
 	}
 
+	count = 0;
 	// Emit code to pass implied parameters
 	if (Function->Variants[0].Flags & VARF_Method)
 	{
@@ -5958,7 +5982,7 @@ ExpEmit FxVMFunctionCall::Emit(VMFunctionBuilder *build)
 	{
 		for (unsigned i = 0; i < ArgList->Size(); ++i)
 		{
-			EmitParameter(build, (*ArgList)[i], ScriptPosition);
+			count += EmitParameter(build, (*ArgList)[i], ScriptPosition);
 		}
 	}
 	// Get a constant register for this function
diff --git a/src/scripting/vm/vm.h b/src/scripting/vm/vm.h
index c14a8a6e5..4eb055e6e 100644
--- a/src/scripting/vm/vm.h
+++ b/src/scripting/vm/vm.h
@@ -134,7 +134,9 @@ enum
 	REGT_TYPE		= 3,
 
 	REGT_KONST		= 4,
-	REGT_MULTIREG	= 8,	// (e.g. a vector)
+	REGT_MULTIREG2	= 8,
+	REGT_MULTIREG3	= 16,	// (e.g. a vector)
+	REGT_MULTIREG	= 24,
 	REGT_ADDROF		= 32,	// used with PARAM: pass address of this register
 
 	REGT_NIL		= 128	// parameter was omitted
diff --git a/src/scripting/vm/vmbuilder.cpp b/src/scripting/vm/vmbuilder.cpp
index dd07d0100..912b95861 100644
--- a/src/scripting/vm/vmbuilder.cpp
+++ b/src/scripting/vm/vmbuilder.cpp
@@ -498,7 +498,11 @@ size_t VMFunctionBuilder::Emit(int opcode, int opa, int opb, int opc)
 	assert(opc >= 0 && opc <= 255);
 	if (opcode == OP_PARAM)
 	{
-		ParamChange(1);
+		int chg;
+		if (opb & REGT_MULTIREG2) chg = 2;
+		else if (opb&REGT_MULTIREG3) chg = 3;
+		else chg = 1;
+		ParamChange(chg);
 	}
 	else if (opcode == OP_CALL || opcode == OP_CALL_K || opcode == OP_TAIL || opcode == OP_TAIL_K)
 	{
diff --git a/src/scripting/vm/vmdisasm.cpp b/src/scripting/vm/vmdisasm.cpp
index c20083dcd..ea199612c 100644
--- a/src/scripting/vm/vmdisasm.cpp
+++ b/src/scripting/vm/vmdisasm.cpp
@@ -578,8 +578,10 @@ static int print_reg(FILE *out, int col, int arg, int mode, int immshift, const
 				return col+printf_wrapper(out, "s%d", regnum);
 			case REGT_POINTER:
 				return col+printf_wrapper(out, "a%d", regnum);
-			case REGT_FLOAT | REGT_MULTIREG:
-				return col+printf_wrapper(out, "v%d", regnum);
+			case REGT_FLOAT | REGT_MULTIREG2:
+				return col+printf_wrapper(out, "v%d.2", regnum);
+			case REGT_FLOAT | REGT_MULTIREG3:
+				return col+printf_wrapper(out, "v%d.3", regnum);
 			case REGT_INT | REGT_KONST:
 				return col+print_reg(out, 0, regnum, MODE_KI, 0, func);
 			case REGT_FLOAT | REGT_KONST:
diff --git a/src/scripting/vm/vmexec.h b/src/scripting/vm/vmexec.h
index 824cd6366..9162ca996 100644
--- a/src/scripting/vm/vmexec.h
+++ b/src/scripting/vm/vmexec.h
@@ -453,7 +453,7 @@ begin:
 			}
 			else
 			{
-				switch(b & (REGT_TYPE | REGT_KONST | REGT_ADDROF))
+				switch(b)
 				{
 				case REGT_INT:
 					assert(C < f->NumRegD);
@@ -492,40 +492,31 @@ begin:
 					::new(param) VMValue(konsta[C].v, konstatag[C]);
 					break;
 				case REGT_FLOAT:
-					if (b & REGT_MULTIREG)
-					{
-						assert(C < f->NumRegF - 2);
-						assert(f->NumParam < sfunc->MaxParam - 1);
-						::new(param) VMValue(reg.f[C]);
-						::new(param+1) VMValue(reg.f[C+1]);
-						::new(param+2) VMValue(reg.f[C+2]);
-						f->NumParam += 2;
-					}
-					else
-					{
-						assert(C < f->NumRegF);
-						::new(param) VMValue(reg.f[C]);
-					}
+					assert(C < f->NumRegF);
+					::new(param) VMValue(reg.f[C]);
+					break;
+				case REGT_FLOAT | REGT_MULTIREG2:
+					assert(C < f->NumRegF - 1);
+					assert(f->NumParam < sfunc->MaxParam);
+					::new(param) VMValue(reg.f[C]);
+					::new(param + 1) VMValue(reg.f[C + 1]);
+					f->NumParam++;
+					break;
+				case REGT_FLOAT | REGT_MULTIREG3:
+					assert(C < f->NumRegF - 2);
+					assert(f->NumParam < sfunc->MaxParam - 1);
+					::new(param) VMValue(reg.f[C]);
+					::new(param + 1) VMValue(reg.f[C + 1]);
+					::new(param + 2) VMValue(reg.f[C + 2]);
+					f->NumParam += 2;
 					break;
 				case REGT_FLOAT | REGT_ADDROF:
 					assert(C < f->NumRegF);
 					::new(param) VMValue(&reg.f[C], ATAG_FREGISTER);
 					break;
 				case REGT_FLOAT | REGT_KONST:
-					if (b & REGT_MULTIREG)
-					{
-						assert(C < sfunc->NumKonstF - 2);
-						assert(f->NumParam < sfunc->MaxParam - 1);
-						::new(param) VMValue(konstf[C]);
-						::new(param+1) VMValue(konstf[C+1]);
-						::new(param+2) VMValue(konstf[C+2]);
-						f->NumParam += 2;
-					}
-					else
-					{
-						assert(C < sfunc->NumKonstF);
-						::new(param) VMValue(konstf[C]);
-					}
+					assert(C < sfunc->NumKonstF);
+					::new(param) VMValue(konstf[C]);
 					break;
 				default:
 					assert(0);
diff --git a/src/scripting/zscript/zcc_compile.cpp b/src/scripting/zscript/zcc_compile.cpp
index 294763f9b..f2644b240 100644
--- a/src/scripting/zscript/zcc_compile.cpp
+++ b/src/scripting/zscript/zcc_compile.cpp
@@ -2017,6 +2017,7 @@ void ZCCCompiler::InitFunctions()
 				SetImplicitArgs(&args, &argflags, &argnames, c->Type(), varflags);
 				argdefaults.Resize(argnames.Size());
 				auto p = f->Params;
+				bool hasoptionals = false;
 				if (p != nullptr)
 				{
 					do
@@ -2043,6 +2044,7 @@ void ZCCCompiler::InitFunctions()
 							else if (p->Default != nullptr)
 							{
 								flags |= VARF_Optional;
+								hasoptionals = true;
 								// The simplifier is not suited to convert the constant into something usable. 
 								// All it does is reduce the expression to a constant but we still got to do proper type checking and conversion.
 								// It will also lose important type info about enums, once these get implemented
@@ -2094,6 +2096,10 @@ void ZCCCompiler::InitFunctions()
 								}
 								if (x != nullptr) delete x;
 							}
+							else if (hasoptionals)
+							{
+								Error(p, "All arguments after the first optional one need also be optional.");
+							}
 							// TBD: disallow certain types? For now, let everything pass that isn't an array.
 							args.Push(type);
 							argflags.Push(flags);