diff --git a/api.go b/api.go
index 62375d1..aa32298 100644
--- a/api.go
+++ b/api.go
@@ -6,19 +6,19 @@ func newConn(module api.Module) *Conn {
 	getFun := func(name string) api.Function {
 		f := module.ExportedFunction(name)
 		if f == nil {
-			panic("sqlite3: could not find " + name + " function")
+			panic(noFuncErr + errorString(name))
 		}
 		return f
 	}
 
 	global := module.ExportedGlobal("malloc_destructor")
 	if global == nil {
-		panic("sqlite3: could not find malloc_destructor global")
+		panic(noGlobalErr + "malloc_destructor")
 	}
 	destructor := uint32(global.Get())
 	destructor, ok := module.Memory().ReadUint32Le(destructor)
 	if !ok {
-		panic("sqlite3: could not read malloc_destructor global")
+		panic(noGlobalErr + "malloc_destructor")
 	}
 
 	return &Conn{
diff --git a/conn.go b/conn.go
index df5816e..203e6e0 100644
--- a/conn.go
+++ b/conn.go
@@ -184,7 +184,7 @@ func (c *Conn) new(len uint32) uint32 {
 		panic(err)
 	}
 	if r[0] == 0 {
-		panic("sqlite3: out of memory")
+		panic(oomErr)
 	}
 	return uint32(r[0])
 }
@@ -199,7 +199,7 @@ func (c *Conn) newBytes(s []byte) uint32 {
 	mem, ok := c.memory.Read(ptr, siz)
 	if !ok {
 		c.api.free.Call(c.ctx, uint64(ptr))
-		panic("sqlite3: out of range")
+		panic(rangeErr)
 	}
 
 	copy(mem, s)
@@ -212,7 +212,7 @@ func (c *Conn) newString(s string) uint32 {
 	mem, ok := c.memory.Read(ptr, siz)
 	if !ok {
 		c.api.free.Call(c.ctx, uint64(ptr))
-		panic("sqlite3: out of range")
+		panic(rangeErr)
 	}
 
 	mem[len(s)] = 0
@@ -227,15 +227,13 @@ func (c *Conn) getString(ptr, maxlen uint32) string {
 func getString(memory api.Memory, ptr, maxlen uint32) string {
 	mem, ok := memory.Read(ptr, maxlen)
 	if !ok {
-		if size := memory.Size(); ptr < size {
-			mem, ok = memory.Read(ptr, size-ptr)
-		}
+		mem, ok = memory.Read(ptr, memory.Size()-ptr)
 		if !ok {
-			panic("sqlite3: out of range")
+			panic(rangeErr)
 		}
 	}
 	if i := bytes.IndexByte(mem, 0); i < 0 {
-		panic("sqlite3: missing NUL terminator")
+		panic(noNulErr)
 	} else {
 		return string(mem[:i])
 	}
diff --git a/error.go b/error.go
index 36b5158..3461017 100644
--- a/error.go
+++ b/error.go
@@ -30,3 +30,15 @@ func (e Error) Error() string {
 
 	return b.String()
 }
+
+type errorString string
+
+func (e errorString) Error() string { return string(e) }
+
+const (
+	oomErr      = errorString("sqlite3: out of memory")
+	rangeErr    = errorString("sqlite3: index out of range")
+	noNulErr    = errorString("sqlite3: missing NUL terminator")
+	noGlobalErr = errorString("sqlite3: could not find global: ")
+	noFuncErr   = errorString("sqlite3: could not find function: ")
+)
diff --git a/stmt.go b/stmt.go
index 13df004..0df44b2 100644
--- a/stmt.go
+++ b/stmt.go
@@ -153,7 +153,7 @@ func (s *Stmt) ColumnText(col int) string {
 
 	mem, ok := s.c.memory.Read(ptr, uint32(r[0]))
 	if !ok {
-		panic("sqlite3: out of range")
+		panic(rangeErr)
 	}
 	return string(mem)
 }
@@ -179,7 +179,7 @@ func (s *Stmt) ColumnBlob(col int, buf []byte) int {
 
 	mem, ok := s.c.memory.Read(ptr, uint32(r[0]))
 	if !ok {
-		panic("sqlite3: out of range")
+		panic(rangeErr)
 	}
 	return copy(mem, buf)
 }
diff --git a/vfs.go b/vfs.go
index e8a015b..2c3f02e 100644
--- a/vfs.go
+++ b/vfs.go
@@ -54,7 +54,7 @@ func vfsExit(ctx context.Context, mod api.Module, exitCode uint32) {
 func vfsRandomness(ctx context.Context, mod api.Module, vfs, nByte, zOut uint32) uint32 {
 	mem, ok := mod.Memory().Read(zOut, nByte)
 	if !ok {
-		return 0
+		panic(rangeErr)
 	}
 	n, _ := rand.Read(mem)
 	return uint32(n)
@@ -67,9 +67,8 @@ func vfsSleep(ctx context.Context, vfs, microseconds uint32) uint32 {
 
 func vfsCurrentTime(ctx context.Context, mod api.Module, vfs, out uint32) uint32 {
 	day := julianday.Float(time.Now())
-	ok := mod.Memory().WriteFloat64Le(out, day)
-	if !ok {
-		return uint32(ERROR)
+	if ok := mod.Memory().WriteFloat64Le(out, day); !ok {
+		panic(rangeErr)
 	}
 	return _OK
 }
@@ -77,9 +76,8 @@ func vfsCurrentTime(ctx context.Context, mod api.Module, vfs, out uint32) uint32
 func vfsCurrentTime64(ctx context.Context, mod api.Module, vfs, out uint32) uint32 {
 	day, nsec := julianday.Date(time.Now())
 	msec := day*86_400_000 + nsec/1_000_000
-	ok := mod.Memory().WriteUint64Le(out, uint64(msec))
-	if !ok {
-		return uint32(ERROR)
+	if ok := mod.Memory().WriteUint64Le(out, uint64(msec)); !ok {
+		panic(rangeErr)
 	}
 	return _OK
 }
@@ -92,12 +90,12 @@ func vfsFullPathname(ctx context.Context, mod api.Module, vfs, zName, nOut, zOut
 	}
 
 	siz := uint32(len(s) + 1)
-	if siz > zOut {
+	if siz > nOut {
 		return uint32(IOERR)
 	}
 	mem, ok := mod.Memory().Read(zOut, siz)
 	if !ok {
-		return uint32(IOERR)
+		panic(rangeErr)
 	}
 
 	mem[len(s)] = 0
@@ -160,9 +158,8 @@ func vfsAccess(ctx context.Context, mod api.Module, vfs, zName, flags, pResOut u
 		return uint32(IOERR_ACCESS)
 	}
 
-	ok := mod.Memory().WriteUint32Le(pResOut, res)
-	if !ok {
-		panic("sqlite: out-of-range")
+	if ok := mod.Memory().WriteUint32Le(pResOut, res); !ok {
+		panic(rangeErr)
 	}
 	return _OK
 }
@@ -201,9 +198,8 @@ func vfsOpen(ctx context.Context, mod api.Module, vfs, zName, file, flags, pOutF
 	c.files = append(c.files, f)
 found:
 
-	ok := mod.Memory().WriteUint32Le(file+ptrSize, uint32(id))
-	if !ok {
-		panic("sqlite: out-of-range")
+	if ok := mod.Memory().WriteUint32Le(file+ptrSize, uint32(id)); !ok {
+		panic(rangeErr)
 	}
 	return _OK
 }
@@ -211,7 +207,7 @@ found:
 func vfsClose(ctx context.Context, mod api.Module, file uint32) uint32 {
 	id, ok := mod.Memory().ReadUint32Le(file + ptrSize)
 	if !ok {
-		panic("sqlite: out-of-range")
+		panic(rangeErr)
 	}
 
 	c := ctx.Value(connContext{}).(*Conn)
@@ -226,12 +222,12 @@ func vfsClose(ctx context.Context, mod api.Module, file uint32) uint32 {
 func vfsRead(ctx context.Context, mod api.Module, file, buf, iAmt uint32, iOfst uint64) uint32 {
 	id, ok := mod.Memory().ReadUint32Le(file + ptrSize)
 	if !ok {
-		panic("sqlite: out-of-range")
+		panic(rangeErr)
 	}
 
 	mem, ok := mod.Memory().Read(buf, iAmt)
 	if !ok {
-		panic("sqlite: out-of-range")
+		panic(rangeErr)
 	}
 
 	c := ctx.Value(connContext{}).(*Conn)
@@ -251,12 +247,12 @@ func vfsRead(ctx context.Context, mod api.Module, file, buf, iAmt uint32, iOfst
 func vfsWrite(ctx context.Context, mod api.Module, file, buf, iAmt uint32, iOfst uint64) uint32 {
 	id, ok := mod.Memory().ReadUint32Le(file + ptrSize)
 	if !ok {
-		panic("sqlite: out-of-range")
+		panic(rangeErr)
 	}
 
 	mem, ok := mod.Memory().Read(buf, iAmt)
 	if !ok {
-		panic("sqlite: out-of-range")
+		panic(rangeErr)
 	}
 
 	c := ctx.Value(connContext{}).(*Conn)
@@ -270,7 +266,7 @@ func vfsWrite(ctx context.Context, mod api.Module, file, buf, iAmt uint32, iOfst
 func vfsTruncate(ctx context.Context, mod api.Module, file uint32, size uint64) uint32 {
 	id, ok := mod.Memory().ReadUint32Le(file + ptrSize)
 	if !ok {
-		panic("sqlite: out-of-range")
+		panic(rangeErr)
 	}
 
 	c := ctx.Value(connContext{}).(*Conn)
@@ -284,7 +280,7 @@ func vfsTruncate(ctx context.Context, mod api.Module, file uint32, size uint64)
 func vfsSync(ctx context.Context, mod api.Module, file, flags uint32) uint32 {
 	id, ok := mod.Memory().ReadUint32Le(file + ptrSize)
 	if !ok {
-		panic("sqlite: out-of-range")
+		panic(rangeErr)
 	}
 
 	c := ctx.Value(connContext{}).(*Conn)
@@ -298,7 +294,7 @@ func vfsSync(ctx context.Context, mod api.Module, file, flags uint32) uint32 {
 func vfsFileSize(ctx context.Context, mod api.Module, file, pSize uint32) uint32 {
 	id, ok := mod.Memory().ReadUint32Le(file + ptrSize)
 	if !ok {
-		panic("sqlite: out-of-range")
+		panic(rangeErr)
 	}
 
 	c := ctx.Value(connContext{}).(*Conn)
@@ -307,9 +303,8 @@ func vfsFileSize(ctx context.Context, mod api.Module, file, pSize uint32) uint32
 		return uint32(IOERR_SEEK)
 	}
 
-	ok = mod.Memory().WriteUint64Le(pSize, uint64(off))
-	if !ok {
-		panic("sqlite: out-of-range")
+	if ok := mod.Memory().WriteUint64Le(pSize, uint64(off)); !ok {
+		panic(rangeErr)
 	}
 	return _OK
 }