diff --git a/_generated/generics.go b/_generated/generics.go
index 3f402f21..fa480d39 100644
--- a/_generated/generics.go
+++ b/_generated/generics.go
@@ -78,6 +78,11 @@ type GenericTestTwo[A, B any, AP msgp.RTFor[A], BP msgp.RTFor[B]] struct {
 	GP2 map[string]*GenericTest2[B, BP, string] `msg:",allownil"`
 }
 
+type GenericTest3List[A, B any, AP msgp.RTFor[A], BP msgp.RTFor[B]] []GenericTest3[A, B, AP, BP]
+type GenericTest3Map[A, B any, AP msgp.RTFor[A], BP msgp.RTFor[B]] map[string]GenericTest3[A, B, AP, BP]
+
+type GenericTest3Array[A, B any, AP msgp.RTFor[A], BP msgp.RTFor[B]] [5]GenericTest3[A, B, AP, BP]
+
 type GenericTest3[A, B any, _ msgp.RTFor[A], _ msgp.RTFor[B]] struct {
 	A A
 	B B
diff --git a/_generated/generics_test.go b/_generated/generics_test.go
index a669859e..6f8396fd 100644
--- a/_generated/generics_test.go
+++ b/_generated/generics_test.go
@@ -63,3 +63,83 @@ func TestGenericsEncode(t *testing.T) {
 		t.Errorf("\n got=%#v\nwant=%#v", got, x)
 	}
 }
+
+// Test for generic alias types (slices, maps, arrays) - these verify the type parameter fix
+func TestGenericTest3List(t *testing.T) {
+	// Test GenericTest3List
+	list := GenericTest3List[Fixed, Fixed, *Fixed, *Fixed]{
+		{A: Fixed{A: 1.5}, B: Fixed{A: 2.5}},
+		{A: Fixed{A: 3.5}, B: Fixed{A: 4.5}},
+	}
+
+	// Test marshaling
+	data, err := list.MarshalMsg(nil)
+	if err != nil {
+		t.Fatalf("GenericTest3List.MarshalMsg failed: %v", err)
+	}
+
+	// Test unmarshaling
+	var list2 GenericTest3List[Fixed, Fixed, *Fixed, *Fixed]
+	_, err = list2.UnmarshalMsg(data)
+	if err != nil {
+		t.Fatalf("GenericTest3List.UnmarshalMsg failed: %v", err)
+	}
+
+	// Verify round-trip
+	if len(list2) != 2 || list2[0].A.A != 1.5 || list2[0].B.A != 2.5 {
+		t.Errorf("GenericTest3List round-trip failed")
+	}
+}
+
+func TestGenericTest3Map(t *testing.T) {
+	// Test GenericTest3Map
+	testMap := GenericTest3Map[Fixed, Fixed, *Fixed, *Fixed]{
+		"key1": {A: Fixed{A: 1.5}, B: Fixed{A: 2.5}},
+		"key2": {A: Fixed{A: 3.5}, B: Fixed{A: 4.5}},
+	}
+
+	// Test marshaling
+	data, err := testMap.MarshalMsg(nil)
+	if err != nil {
+		t.Fatalf("GenericTest3Map.MarshalMsg failed: %v", err)
+	}
+
+	// Test unmarshaling
+	var testMap2 GenericTest3Map[Fixed, Fixed, *Fixed, *Fixed]
+	_, err = testMap2.UnmarshalMsg(data)
+	if err != nil {
+		t.Fatalf("GenericTest3Map.UnmarshalMsg failed: %v", err)
+	}
+
+	// Verify round-trip
+	if len(testMap2) != 2 || testMap2["key1"].A.A != 1.5 || testMap2["key1"].B.A != 2.5 {
+		t.Errorf("GenericTest3Map round-trip failed")
+	}
+}
+
+func TestGenericTest3Array(t *testing.T) {
+	// Test GenericTest3Array
+	testArray := GenericTest3Array[Fixed, Fixed, *Fixed, *Fixed]{
+		{A: Fixed{A: 1.5}, B: Fixed{A: 2.5}},
+		{A: Fixed{A: 3.5}, B: Fixed{A: 4.5}},
+		{A: Fixed{A: 5.5}, B: Fixed{A: 6.5}},
+	}
+
+	// Test marshaling
+	data, err := testArray.MarshalMsg(nil)
+	if err != nil {
+		t.Fatalf("GenericTest3Array.MarshalMsg failed: %v", err)
+	}
+
+	// Test unmarshaling
+	var testArray2 GenericTest3Array[Fixed, Fixed, *Fixed, *Fixed]
+	_, err = testArray2.UnmarshalMsg(data)
+	if err != nil {
+		t.Fatalf("GenericTest3Array.UnmarshalMsg failed: %v", err)
+	}
+
+	// Verify round-trip
+	if testArray2[0].A.A != 1.5 || testArray2[0].B.A != 2.5 || testArray2[2].A.A != 5.5 {
+		t.Errorf("GenericTest3Array round-trip failed")
+	}
+}
diff --git a/gen/decode.go b/gen/decode.go
index 07352c6e..5197b854 100644
--- a/gen/decode.go
+++ b/gen/decode.go
@@ -225,14 +225,15 @@ func (d *decodeGen) gBase(b *BaseElem) {
 		if b.typeParams.isPtr {
 			dst = "*" + dst
 		}
+
 		if b.Convert {
-			if remap := b.typeParams.ToPointerMap[dst]; remap != "" {
+			if remap := b.typeParams.ToPointerMap[stripTypeParams(dst)]; remap != "" {
 				vname = fmt.Sprintf(remap, vname)
 			}
 			lowered := b.ToBase() + "(" + vname + ")"
 			d.p.printf("\nerr = %s.DecodeMsg(dc)", lowered)
 		} else {
-			if remap := b.typeParams.ToPointerMap[dst]; remap != "" {
+			if remap := b.typeParams.ToPointerMap[stripTypeParams(dst)]; remap != "" {
 				vname = fmt.Sprintf(remap, vname)
 			}
 			d.p.printf("\nerr = %s.DecodeMsg(dc)", vname)
diff --git a/gen/elem.go b/gen/elem.go
index bcf3c0e6..dd757273 100644
--- a/gen/elem.go
+++ b/gen/elem.go
@@ -160,14 +160,42 @@ type GenericTypeParams struct {
 	isPtr        bool
 }
 
-func (c *common) SetVarname(s string)                { c.vname = s }
-func (c *common) Varname() string                    { return c.vname }
+func (c *common) SetVarname(s string) { c.vname = s }
+func (c *common) Varname() string     { return c.vname }
+
+// typeNameWithParams returns the type name with generic parameters appended if they exist
+// stripTypeParams removes type parameters from a type name for lookup purposes
+// e.g. "MyType[T, U]" becomes "MyType", "*SomeType[A]" becomes "*SomeType"
+func stripTypeParams(typeName string) string {
+	if idx := strings.Index(typeName, "["); idx != -1 {
+		return typeName[:idx]
+	}
+	return typeName
+}
+
+func (c *common) typeNameWithParams(baseName string) string {
+	if c.typeParams.TypeParams != "" && !strings.Contains(baseName, "[") {
+		// Check if baseName is a single identifier without dots (likely a type parameter)
+		if !strings.Contains(baseName, ".") && len(baseName) <= 2 && len(baseName) > 0 {
+			// This looks like a simple type parameter, don't add type parameters
+			return baseName
+		}
+		return baseName + c.typeParams.TypeParams
+	}
+	return baseName
+}
+
+// baseTypeName returns the type name without generic parameters (for use in method receivers)
+func (c *common) baseTypeName() string {
+	return c.alias
+}
 func (c *common) Alias(typ string)                   { c.alias = typ }
 func (c *common) hidden()                            {}
 func (c *common) AllowNil() bool                     { return false }
 func (c *common) SetIsAllowNil(bool)                 {}
 func (c *common) SetTypeParams(tp GenericTypeParams) { c.typeParams = tp }
 func (c *common) TypeParams() GenericTypeParams      { return c.typeParams }
+func (c *common) BaseTypeName() string               { return c.baseTypeName() }
 func (c *common) AlwaysPtr(set *bool) bool {
 	if c != nil && set != nil {
 		c.ptrRcv = *set
@@ -245,6 +273,9 @@ type Elem interface {
 	// TypeParams returns the generic type parameters for this element
 	TypeParams() GenericTypeParams
 
+	// BaseTypeName returns the type name without generic parameters
+	BaseTypeName() string
+
 	hidden()
 }
 
@@ -283,10 +314,10 @@ ridx:
 
 func (a *Array) TypeName() string {
 	if a.alias != "" {
-		return a.alias
+		return a.typeNameWithParams(a.alias)
 	}
 	a.Alias(fmt.Sprintf("[%s]%s", a.Size, a.Els.TypeName()))
-	return a.alias
+	return a.typeNameWithParams(a.alias)
 }
 
 func (a *Array) Copy() Elem {
@@ -335,14 +366,14 @@ ridx:
 
 func (m *Map) TypeName() string {
 	if m.alias != "" {
-		return m.alias
+		return m.typeNameWithParams(m.alias)
 	}
 	keyType := "string"
 	if m.Key != nil {
 		keyType = m.Key.TypeName()
 	}
 	m.Alias("map[" + keyType + "]" + m.Value.TypeName())
-	return m.alias
+	return m.typeNameWithParams(m.alias)
 }
 
 func (m *Map) Copy() Elem {
@@ -403,10 +434,10 @@ func (s *Slice) SetVarname(a string) {
 
 func (s *Slice) TypeName() string {
 	if s.alias != "" {
-		return s.alias
+		return s.typeNameWithParams(s.alias)
 	}
 	s.Alias("[]" + s.Els.TypeName())
-	return s.alias
+	return s.typeNameWithParams(s.alias)
 }
 
 func (s *Slice) Copy() Elem {
@@ -480,10 +511,10 @@ func (s *Ptr) SetVarname(a string) {
 
 func (s *Ptr) TypeName() string {
 	if s.alias != "" {
-		return s.alias
+		return s.typeNameWithParams(s.alias)
 	}
 	s.Alias("*" + s.Value.TypeName())
-	return s.alias
+	return s.typeNameWithParams(s.alias)
 }
 
 func (s *Ptr) Copy() Elem {
@@ -673,10 +704,10 @@ func (s *BaseElem) SetVarname(a string) {
 // type name for the base element.
 func (s *BaseElem) TypeName() string {
 	if s.alias != "" {
-		return s.alias
+		return s.typeNameWithParams(s.alias)
 	}
 	s.common.Alias(s.BaseType())
-	return s.alias
+	return s.typeNameWithParams(s.alias)
 }
 
 // ToBase, used if Convert==true, is used as tmp = {{ToBase}}({{Varname}})
@@ -715,7 +746,7 @@ func (s *BaseElem) BaseName() string {
 func (s *BaseElem) BaseType() string {
 	switch s.Value {
 	case IDENT:
-		return s.TypeName()
+		return s.alias
 
 	// exceptions to the naming/capitalization
 	// rule:
diff --git a/gen/encode.go b/gen/encode.go
index 2b8bd7e8..44f5ca57 100644
--- a/gen/encode.go
+++ b/gen/encode.go
@@ -344,7 +344,14 @@ func (e *encodeGen) gBase(b *BaseElem) {
 		if b.typeParams.isPtr {
 			dst = "*" + dst
 		}
-		if remap := b.typeParams.ToPointerMap[dst]; remap != "" {
+
+		// Strip type parameters from dst for lookup in ToPointerMap
+		lookupKey := stripTypeParams(dst)
+		if idx := strings.Index(dst, "["); idx != -1 {
+			lookupKey = dst[:idx]
+		}
+
+		if remap := b.typeParams.ToPointerMap[lookupKey]; remap != "" {
 			vname = fmt.Sprintf(remap, vname)
 		}
 		e.p.printf("\nerr = %s.EncodeMsg(en)", vname)
diff --git a/gen/marshal.go b/gen/marshal.go
index e68464ad..acd3c018 100644
--- a/gen/marshal.go
+++ b/gen/marshal.go
@@ -358,7 +358,7 @@ func (m *marshalGen) gBase(b *BaseElem) {
 		if b.typeParams.isPtr {
 			dst = "*" + dst
 		}
-		if remap := b.typeParams.ToPointerMap[dst]; remap != "" {
+		if remap := b.typeParams.ToPointerMap[stripTypeParams(dst)]; remap != "" {
 			vname = fmt.Sprintf(remap, vname)
 		}
 		echeck = true
diff --git a/gen/size.go b/gen/size.go
index 53504d8d..3efab37d 100644
--- a/gen/size.go
+++ b/gen/size.go
@@ -247,7 +247,14 @@ func (s *sizeGen) gBase(b *BaseElem) {
 		if b.typeParams.isPtr {
 			dst = "*" + dst
 		}
-		if remap := b.typeParams.ToPointerMap[dst]; remap != "" {
+
+		// Strip type parameters from dst for lookup in ToPointerMap
+		lookupKey := stripTypeParams(dst)
+		if idx := strings.Index(dst, "["); idx != -1 {
+			lookupKey = dst[:idx]
+		}
+
+		if remap := b.typeParams.ToPointerMap[lookupKey]; remap != "" {
 			vname = fmt.Sprintf(remap, vname)
 		}
 		s.addConstant(basesizeExpr(b.Value, vname, b.BaseName()))
diff --git a/gen/spec.go b/gen/spec.go
index 4ff4fbee..0e02036d 100644
--- a/gen/spec.go
+++ b/gen/spec.go
@@ -268,7 +268,7 @@ func next(t traversal, e Elem) {
 
 // possibly-immutable method receiver
 func imutMethodReceiver(p Elem) string {
-	typeName := p.TypeName()
+	typeName := p.BaseTypeName()
 	typeParams := p.TypeParams()
 
 	switch e := p.(type) {
@@ -300,7 +300,7 @@ func imutMethodReceiver(p Elem) string {
 // so that its method receiver
 // is of the write type.
 func methodReceiver(p Elem) string {
-	typeName := p.TypeName()
+	typeName := p.BaseTypeName()
 	typeParams := p.TypeParams()
 
 	switch p.(type) {
diff --git a/gen/unmarshal.go b/gen/unmarshal.go
index f1d6bfce..f972d359 100644
--- a/gen/unmarshal.go
+++ b/gen/unmarshal.go
@@ -247,10 +247,9 @@ func (u *unmarshalGen) gBase(b *BaseElem) {
 		if b.typeParams.isPtr {
 			dst = "*" + dst
 		}
-		if remap := b.typeParams.ToPointerMap[dst]; remap != "" {
+		if remap := b.typeParams.ToPointerMap[stripTypeParams(dst)]; remap != "" {
 			lowered = fmt.Sprintf(remap, lowered)
 		}
-
 		u.p.printf("\nbts, err = %s.UnmarshalMsg(bts)", lowered)
 	case Time:
 		if u.ctx.asUTC {