diff --git a/compiler/check.go b/compiler/check.go
index 356d0296..97bb4459 100644
--- a/compiler/check.go
+++ b/compiler/check.go
@@ -10,14 +10,10 @@ import (
 	"tinygo.org/x/go-llvm"
 )
 
-func (c *Compiler) checkType(t llvm.Type, checked map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) {
-	if t.IsNil() {
-		panic(t)
-	}
-
+func (c *Compiler) checkType(t llvm.Type, checked map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) error {
 	// prevent infinite recursion for self-referential types
 	if _, ok := checked[t]; ok {
-		return
+		return nil
 	}
 	checked[t] = struct{}{}
 
@@ -27,10 +23,10 @@ func (c *Compiler) checkType(t llvm.Type, checked map[llvm.Type]struct{}, specia
 		// this is correct
 	case t.Context() == llvm.GlobalContext():
 		// somewhere we accidentally used the global context instead of a real context
-		panic(fmt.Errorf("type %q uses global context", t.String()))
+		return fmt.Errorf("type %q uses global context", t.String())
 	default:
 		// we used some other context by accident
-		panic(fmt.Errorf("type %q uses context %v instead of the main context %v", t.Context(), c.ctx))
+		return fmt.Errorf("type %q uses context %v instead of the main context %v", t.Context(), c.ctx)
 	}
 
 	// if this is a composite type, check the components of the type
@@ -40,7 +36,7 @@ func (c *Compiler) checkType(t llvm.Type, checked map[llvm.Type]struct{}, specia
 		if s, ok := specials[t.TypeKind()]; !ok {
 			specials[t.TypeKind()] = t
 		} else if s != t {
-			panic(fmt.Errorf("duplicate special type %q: %v and %v", t.TypeKind().String(), t, s))
+			return fmt.Errorf("duplicate special type %q: %v and %v", t.TypeKind().String(), t, s)
 		}
 	case llvm.FloatTypeKind, llvm.DoubleTypeKind, llvm.X86_FP80TypeKind, llvm.FP128TypeKind, llvm.PPC_FP128TypeKind:
 		// floating point numbers are primitives - nothing to recurse
@@ -48,81 +44,130 @@ func (c *Compiler) checkType(t llvm.Type, checked map[llvm.Type]struct{}, specia
 		// integers are primitives - nothing to recurse
 	case llvm.FunctionTypeKind:
 		// check arguments and return(s)
-		for _, v := range t.ParamTypes() {
-			c.checkType(v, checked, specials)
+		for i, v := range t.ParamTypes() {
+			if err := c.checkType(v, checked, specials); err != nil {
+				return fmt.Errorf("failed to verify argument %d of type %s: %s", i, t.String(), err.Error())
+			}
+		}
+		if err := c.checkType(t.ReturnType(), checked, specials); err != nil {
+			return fmt.Errorf("failed to verify return type of type %s: %s", t.String(), err.Error())
 		}
-		c.checkType(t.ReturnType(), checked, specials)
 	case llvm.StructTypeKind:
 		// check all elements
-		for _, v := range t.StructElementTypes() {
-			c.checkType(v, checked, specials)
+		for i, v := range t.StructElementTypes() {
+			if err := c.checkType(v, checked, specials); err != nil {
+				return fmt.Errorf("failed to verify type of field %d of struct type %s: %s", i, t.String(), err.Error())
+			}
 		}
 	case llvm.ArrayTypeKind:
 		// check element type
-		c.checkType(t.ElementType(), checked, specials)
+		if err := c.checkType(t.ElementType(), checked, specials); err != nil {
+			return fmt.Errorf("failed to verify element type of array type %s: %s", t.String(), err.Error())
+		}
 	case llvm.PointerTypeKind:
 		// check underlying type
-		c.checkType(t.ElementType(), checked, specials)
+		if err := c.checkType(t.ElementType(), checked, specials); err != nil {
+			return fmt.Errorf("failed to verify underlying type of pointer type %s: %s", t.String(), err.Error())
+		}
 	case llvm.VectorTypeKind:
 		// check element type
-		c.checkType(t.ElementType(), checked, specials)
+		if err := c.checkType(t.ElementType(), checked, specials); err != nil {
+			return fmt.Errorf("failed to verify element type of vector type %s: %s", t.String(), err.Error())
+		}
+	default:
+		return fmt.Errorf("unrecognized kind %q of type %s", t.TypeKind(), t.String())
 	}
+
+	return nil
 }
 
-func (c *Compiler) checkValue(v llvm.Value, types map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) {
+func (c *Compiler) checkValue(v llvm.Value, types map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) error {
 	// check type
-	c.checkType(v.Type(), types, specials)
+	if err := c.checkType(v.Type(), types, specials); err != nil {
+		return fmt.Errorf("failed to verify type of value: %s", err.Error())
+	}
+
+	// check if this is an undefined void
+	if v.IsUndef() && v.Type().TypeKind() == llvm.VoidTypeKind {
+		return errors.New("encountered undefined void value")
+	}
+
+	return nil
 }
 
-func (c *Compiler) checkInstruction(inst llvm.Value, types map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) {
+func (c *Compiler) checkInstruction(inst llvm.Value, types map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) error {
 	// check value properties
-	c.checkValue(inst, types, specials)
+	if err := c.checkValue(inst, types, specials); err != nil {
+		return fmt.Errorf("failed to validate value of instruction %q: %s", inst.Name(), err.Error())
+	}
 
 	// check operands
 	for i := 0; i < inst.OperandsCount(); i++ {
-		c.checkValue(inst.Operand(i), types, specials)
+		if err := c.checkValue(inst.Operand(i), types, specials); err != nil {
+			return fmt.Errorf("failed to validate argument %d of instruction %q: %s", i, inst.Name(), err.Error())
+		}
 	}
+
+	return nil
 }
 
-func (c *Compiler) checkBasicBlock(bb llvm.BasicBlock, types map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) {
+func (c *Compiler) checkBasicBlock(bb llvm.BasicBlock, types map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) error {
 	// check basic block value and type
-	c.checkValue(bb.AsValue(), types, specials)
+	if err := c.checkValue(bb.AsValue(), types, specials); err != nil {
+		return fmt.Errorf("failed to validate value of basic block %s: %s", bb.AsValue().Name(), err.Error())
+	}
 
 	// check instructions
 	for inst := bb.FirstInstruction(); !inst.IsNil(); inst = llvm.NextInstruction(inst) {
-		c.checkInstruction(inst, types, specials)
+		if err := c.checkInstruction(inst, types, specials); err != nil {
+			return fmt.Errorf("failed to validate basic block %q: %s", bb.AsValue().Name(), err.Error())
+		}
 	}
+
+	return nil
 }
 
-func (c *Compiler) checkFunction(fn llvm.Value, types map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) {
+func (c *Compiler) checkFunction(fn llvm.Value, types map[llvm.Type]struct{}, specials map[llvm.TypeKind]llvm.Type) error {
 	// check function value and type
-	c.checkValue(fn, types, specials)
+	if err := c.checkValue(fn, types, specials); err != nil {
+		return fmt.Errorf("failed to validate value of function %s: %s", fn.Name(), err.Error())
+	}
 
 	// check basic blocks
 	for bb := fn.FirstBasicBlock(); !bb.IsNil(); bb = llvm.NextBasicBlock(bb) {
-		c.checkBasicBlock(bb, types, specials)
+		if err := c.checkBasicBlock(bb, types, specials); err != nil {
+			return fmt.Errorf("failed to validate basic block of function %s: %s", fn.Name(), err.Error())
+		}
 	}
+
+	return nil
 }
 
-func (c *Compiler) checkModule() {
+func (c *Compiler) checkModule() error {
 	// check for any context mismatches
 	switch {
 	case c.mod.Context() == c.ctx:
 		// this is correct
 	case c.mod.Context() == llvm.GlobalContext():
 		// somewhere we accidentally used the global context instead of a real context
-		panic(errors.New("module uses global context"))
+		return errors.New("module uses global context")
 	default:
 		// we used some other context by accident
-		panic(fmt.Errorf("module uses context %v instead of the main context %v", c.mod.Context(), c.ctx))
+		return fmt.Errorf("module uses context %v instead of the main context %v", c.mod.Context(), c.ctx)
 	}
 
 	types := map[llvm.Type]struct{}{}
 	specials := map[llvm.TypeKind]llvm.Type{}
 	for fn := c.mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
-		c.checkFunction(fn, types, specials)
+		if err := c.checkFunction(fn, types, specials); err != nil {
+			return err
+		}
 	}
 	for g := c.mod.FirstGlobal(); !g.IsNil(); g = llvm.NextGlobal(g) {
-		c.checkValue(g, types, specials)
+		if err := c.checkValue(g, types, specials); err != nil {
+			return fmt.Errorf("failed to verify global %s of module: %s", g.Name(), err.Error())
+		}
 	}
+
+	return nil
 }
diff --git a/compiler/optimizer.go b/compiler/optimizer.go
index dee33447..480d3283 100644
--- a/compiler/optimizer.go
+++ b/compiler/optimizer.go
@@ -25,7 +25,10 @@ func (c *Compiler) Optimize(optLevel, sizeLevel int, inlinerThreshold uint) erro
 
 	// run a check of all of our code
 	if c.VerifyIR {
-		c.checkModule()
+		err := c.checkModule()
+		if err != nil {
+			return err
+		}
 	}
 
 	// Run function passes for each function.
@@ -93,6 +96,11 @@ func (c *Compiler) Optimize(optLevel, sizeLevel int, inlinerThreshold uint) erro
 			return err
 		}
 	}
+	if c.VerifyIR {
+		if err := c.checkModule(); err != nil {
+			return err
+		}
+	}
 	if err := c.Verify(); err != nil {
 		return errors.New("optimizations caused a verification failure")
 	}