diff --git a/internal/shader/stmt.go b/internal/shader/stmt.go
index 508635d2b..3a3f6aeb1 100644
--- a/internal/shader/stmt.go
+++ b/internal/shader/stmt.go
@@ -87,25 +87,38 @@ func (cs *compileState) parseStmt(block *block, fname string, stmt ast.Stmt, inP
 			}
 			stmts = append(stmts, ss...)
 
-			if op == shaderir.ModOp {
-				if lts[0].Main != shaderir.Int || rts[0].Main != shaderir.Int {
-					var wrongType shaderir.Type
-					if lts[0].Main != shaderir.Int {
-						wrongType = lts[0]
-					} else {
-						wrongType = rts[0]
-					}
-					cs.addError(stmt.Pos(), fmt.Sprintf("invalid operation: operator %% not defined on %s", wrongType.String()))
-					return nil, false
-				}
-			}
-
+			// Treat an integer literal as an integer constant value.
 			if rhs[0].Type == shaderir.NumberExpr && rts[0].Main == shaderir.Int {
 				if !cs.forceToInt(stmt, &rhs[0]) {
 					return nil, false
 				}
 			}
 
+			if lts[0].Main != rts[0].Main {
+				switch lts[0].Main {
+				case shaderir.Int:
+					if !cs.forceToInt(stmt, &rhs[0]) {
+						return nil, false
+					}
+				case shaderir.Float:
+					if rhs[0].Const != nil && rhs[0].Const.Kind() == gconstant.Int {
+						rhs[0].Const = gconstant.ToFloat(rhs[0].Const)
+						rhs[0].ConstType = shaderir.ConstTypeFloat
+					} else {
+						cs.addError(stmt.Pos(), fmt.Sprintf("invalid operation: mismatched types %s and %s", lts[0].String(), rts[0].String()))
+						return nil, false
+					}
+				default:
+					cs.addError(stmt.Pos(), fmt.Sprintf("invalid operation: mismatched types %s and %s", lts[0].String(), rts[0].String()))
+					return nil, false
+				}
+			}
+
+			if op == shaderir.ModOp && lts[0].Main != shaderir.Int {
+				cs.addError(stmt.Pos(), fmt.Sprintf("invalid operation: operator %% not defined on %s", lts[0].String()))
+				return nil, false
+			}
+
 			stmts = append(stmts, shaderir.Stmt{
 				Type: shaderir.Assign,
 				Exprs: []shaderir.Expr{
diff --git a/internal/shader/testdata/for.expected.vs b/internal/shader/testdata/for.expected.vs
index 9cb3f640c..b57a48444 100644
--- a/internal/shader/testdata/for.expected.vs
+++ b/internal/shader/testdata/for.expected.vs
@@ -5,11 +5,11 @@ void F0(out vec2 l0) {
 	vec2 l3 = vec2(0);
 	l1 = vec2(0.0);
 	for (int l2 = 0; l2 < 100; l2++) {
-		(l1).x = ((l1).x) + (l2);
+		(l1).x = ((l1).x) + (float(l2));
 	}
 	l3 = vec2(0.0);
 	for (float l4 = 10.0; l4 >= 0.0; l4 -= 2.0) {
-		(l3).x = ((l3).x) + (l4);
+		(l3).x = ((l3).x) + (float(l4));
 	}
 	l0 = l1;
 	return;
diff --git a/internal/shader/testdata/for.go b/internal/shader/testdata/for.go
index 393029037..9ea023152 100644
--- a/internal/shader/testdata/for.go
+++ b/internal/shader/testdata/for.go
@@ -3,11 +3,11 @@ package main
 func Foo() vec2 {
 	v := vec2(0)
 	for i := 0; i < 100; i++ {
-		v.x += i
+		v.x += float(i)
 	}
 	v2 := vec2(0)
 	for i := 10.0; i >= 0; i -= 2 {
-		v2.x += i
+		v2.x += float(i)
 	}
 	_ = v2
 	return v
diff --git a/internal/shader/testdata/for2.expected.vs b/internal/shader/testdata/for2.expected.vs
index 0fa15b435..252bca9fa 100644
--- a/internal/shader/testdata/for2.expected.vs
+++ b/internal/shader/testdata/for2.expected.vs
@@ -5,7 +5,7 @@ void F0(out vec2 l0) {
 	vec2 l3 = vec2(0);
 	l1 = vec2(0.0);
 	for (int l2 = 0; l2 < 100; l2++) {
-		(l1).x = ((l1).x) + (l2);
+		(l1).x = ((l1).x) + (float(l2));
 		if (((l1).x) >= (100.0)) {
 			break;
 		}
diff --git a/internal/shader/testdata/for2.go b/internal/shader/testdata/for2.go
index 5a8a2b53e..faf3644ba 100644
--- a/internal/shader/testdata/for2.go
+++ b/internal/shader/testdata/for2.go
@@ -3,7 +3,7 @@ package main
 func Foo() vec2 {
 	v := vec2(0)
 	for i := 0; i < 100; i++ {
-		v.x += i
+		v.x += float(i)
 		if v.x >= 100 {
 			break
 		}
diff --git a/shader_test.go b/shader_test.go
index d30ac4181..0bb9bfca6 100644
--- a/shader_test.go
+++ b/shader_test.go
@@ -1351,6 +1351,16 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 
 	if _, err := ebiten.NewShader([]byte(`package main
 
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := 2
+	a %= 1.0
+	return vec4(a)
+}`)); err != nil {
+		t.Error(err)
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
 func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 	a := 2
 	a %= 0.5
@@ -1369,3 +1379,65 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 		t.Errorf("error must be non-nil but was nil")
 	}
 }
+
+func TestShaderOperatorAssign(t *testing.T) {
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := 1.0
+	a += 2
+	return vec4(a)
+}`)); err != nil {
+		t.Error(err)
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := 1.0
+	a += 2.0
+	return vec4(a)
+}`)); err != nil {
+		t.Error(err)
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := 1.0
+	a += 2.1
+	return vec4(a)
+}`)); err != nil {
+		t.Error(err)
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := 1
+	a += 2
+	return vec4(a)
+}`)); err != nil {
+		t.Error(err)
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := 1
+	a += 2.0
+	return vec4(a)
+}`)); err != nil {
+		t.Error(err)
+	}
+
+	if _, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	a := 1
+	a += 2.1
+	return vec4(a)
+}`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
+}