diff --git a/go4k/bridge/bridge.go b/go4k/bridge/bridge.go
index 6e127c4..031c8fa 100644
--- a/go4k/bridge/bridge.go
+++ b/go4k/bridge/bridge.go
@@ -3,6 +3,7 @@ package bridge
 import (
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/vsariola/sointu/go4k"
 )
@@ -49,6 +50,27 @@ var opcodeTable = map[string]opTableEntry{
 	"in":         opTableEntry{C.su_in_id, []string{"channel"}},
 }
 
+type RenderError struct {
+	errcode int
+}
+
+func (e *RenderError) Error() string {
+	var reasons []string
+	if e.errcode&0x40 != 0 {
+		reasons = append(reasons, "FPU stack over/underflow")
+	}
+	if e.errcode&0x04 != 0 {
+		reasons = append(reasons, "FPU divide by zero")
+	}
+	if e.errcode&0x01 != 0 {
+		reasons = append(reasons, "FPU invalid operation")
+	}
+	if e.errcode&0x3800 != 0 {
+		reasons = append(reasons, "FPU stack push/pops are not balanced")
+	}
+	return "RenderError: " + strings.Join(reasons, ", ")
+}
+
 // Render renders until the buffer is full or the modulated time is reached, whichever
 // happens first.
 // Parameters:
@@ -74,7 +96,7 @@ func (synth *C.Synth) Render(buffer []float32, maxtime int) (int, int, error) {
 	time := C.int(maxtime)
 	errcode := int(C.su_render(synth, (*C.float)(&buffer[0]), &samples, &time))
 	if errcode > 0 {
-		return -1, -1, errors.New("RenderTime failed")
+		return int(samples), int(time), &RenderError{errcode: errcode}
 	}
 	return int(samples), int(time), nil
 }
diff --git a/go4k/bridge/bridge_test.go b/go4k/bridge/bridge_test.go
index eafa673..adc5c2b 100644
--- a/go4k/bridge/bridge_test.go
+++ b/go4k/bridge/bridge_test.go
@@ -67,3 +67,98 @@ func TestBridge(t *testing.T) {
 		}
 	}
 }
+
+func TestStackUnderflow(t *testing.T) {
+	patch := go4k.Patch{
+		Instruments: []go4k.Instrument{
+			go4k.Instrument{1, []go4k.Unit{
+				go4k.Unit{"pop", map[string]int{}},
+			}}},
+		SampleOffsets: []go4k.SampleOffset{},
+		DelayTimes:    []int{}}
+	synth, err := bridge.Synth(patch)
+	if err != nil {
+		t.Fatalf("bridge compile error: %v", err)
+	}
+	buffer := make([]float32, 2)
+	err = go4k.Render(synth, buffer)
+	if err == nil {
+		t.Fatalf("rendering should have failed due to stack underflow")
+	}
+}
+
+func TestStackBalancing(t *testing.T) {
+	patch := go4k.Patch{
+		Instruments: []go4k.Instrument{
+			go4k.Instrument{1, []go4k.Unit{
+				go4k.Unit{"push", map[string]int{}},
+			}}},
+		SampleOffsets: []go4k.SampleOffset{},
+		DelayTimes:    []int{}}
+	synth, err := bridge.Synth(patch)
+	if err != nil {
+		t.Fatalf("bridge compile error: %v", err)
+	}
+	buffer := make([]float32, 2)
+	err = go4k.Render(synth, buffer)
+	if err == nil {
+		t.Fatalf("rendering should have failed due to unbalanced stack push/pop")
+	}
+}
+
+func TestStackOverflow(t *testing.T) {
+	patch := go4k.Patch{
+		Instruments: []go4k.Instrument{
+			go4k.Instrument{1, []go4k.Unit{
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"pop", map[string]int{}},
+				go4k.Unit{"pop", map[string]int{}},
+				go4k.Unit{"pop", map[string]int{}},
+				go4k.Unit{"pop", map[string]int{}},
+				go4k.Unit{"pop", map[string]int{}},
+				go4k.Unit{"pop", map[string]int{}},
+				go4k.Unit{"pop", map[string]int{}},
+				go4k.Unit{"pop", map[string]int{}},
+				go4k.Unit{"pop", map[string]int{}},
+			}}},
+		SampleOffsets: []go4k.SampleOffset{},
+		DelayTimes:    []int{}}
+	synth, err := bridge.Synth(patch)
+	if err != nil {
+		t.Fatalf("bridge compile error: %v", err)
+	}
+	buffer := make([]float32, 2)
+	err = go4k.Render(synth, buffer)
+	if err == nil {
+		t.Fatalf("rendering should have failed due to stack overflow, despite balanced push/pops")
+	}
+}
+
+func TestDivideByZero(t *testing.T) {
+	patch := go4k.Patch{
+		Instruments: []go4k.Instrument{
+			go4k.Instrument{1, []go4k.Unit{
+				go4k.Unit{"loadval", map[string]int{"value": 128}},
+				go4k.Unit{"invgain", map[string]int{"invgain": 0}},
+				go4k.Unit{"pop", map[string]int{}},
+			}}},
+		SampleOffsets: []go4k.SampleOffset{},
+		DelayTimes:    []int{}}
+	synth, err := bridge.Synth(patch)
+	if err != nil {
+		t.Fatalf("bridge compile error: %v", err)
+	}
+	buffer := make([]float32, 2)
+	err = go4k.Render(synth, buffer)
+	if err == nil {
+		t.Fatalf("rendering should have failed due to divide by zero")
+	}
+}