diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
index 2894834cb..90c7ae4bb 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
@@ -299,7 +299,7 @@ internal class AssignmentAsmGen(private val program: Program,
                     )
                     when (value.operator) {
                         "+" -> {}
-                        "-" -> augmentableAsmGen.inplaceNegate(assign)
+                        "-" -> augmentableAsmGen.inplaceNegate(assign, true)
                         "~" -> augmentableAsmGen.inplaceInvert(assign)
                         else -> throw AssemblyError("invalid prefix operator")
                     }
diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AugmentableAssignmentAsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AugmentableAssignmentAsmGen.kt
index 049e573d4..d0b3abc2e 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AugmentableAssignmentAsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AugmentableAssignmentAsmGen.kt
@@ -23,7 +23,7 @@ internal class AugmentableAssignmentAsmGen(private val program: Program,
                 // A = -A , A = +A, A = ~A, A = not A
                 when (value.operator) {
                     "+" -> {}
-                    "-" -> inplaceNegate(assign)
+                    "-" -> inplaceNegate(assign, false)
                     "~" -> inplaceInvert(assign)
                     else -> throw AssemblyError("invalid prefix operator")
                 }
@@ -1871,9 +1871,16 @@ internal class AugmentableAssignmentAsmGen(private val program: Program,
         }
     }
 
-    internal fun inplaceNegate(assign: AsmAssignment) {
+    internal fun inplaceNegate(assign: AsmAssignment, ignoreDatatype: Boolean) {
         val target = assign.target
-        when (target.datatype) {
+        val datatype = if(ignoreDatatype) {
+            when(target.datatype) {
+                DataType.UBYTE, DataType.BYTE -> DataType.BYTE
+                DataType.UWORD, DataType.WORD -> DataType.WORD
+                else -> target.datatype
+            }
+        } else target.datatype
+        when (datatype) {
             DataType.BYTE -> {
                 when (target.kind) {
                     TargetStorageKind.VARIABLE -> {
diff --git a/compiler/test/codegeneration/TestVariables.kt b/compiler/test/codegeneration/TestVariables.kt
index 8863bcb46..24c425ead 100644
--- a/compiler/test/codegeneration/TestVariables.kt
+++ b/compiler/test/codegeneration/TestVariables.kt
@@ -63,5 +63,21 @@ class TestVariables: FunSpec({
         """
         compileText(C64Target(), false, text, writeAssembly = true) shouldNotBe null
     }
+    
+    test("negation of unsigned via casts") {
+        val text = """
+            main {
+                sub start() {
+                    cx16.r0L = -(cx16.r0L as byte) as ubyte
+                    cx16.r0 = -(cx16.r0 as word) as uword
+                    ubyte ub
+                    uword uw
+                    ub = -(ub as byte) as ubyte
+                    uw = -(uw as word) as uword
+                }
+            }
+        """
+        compileText(C64Target(), false, text, writeAssembly = true) shouldNotBe null
+    }
 
 })
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 1b3f9a55e..62a3eb6dd 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,7 +3,7 @@ TODO
 
 For next release
 ^^^^^^^^^^^^^^^^
-- fix compiler crash cx16.r0 = (-(cx16.r0 as word) as uword)
+- make the adpcm example read wav files directly (so no need anymore to extract the binary frame data from them)
 - duplicate diskio for cx16 (get rid of cx16diskio, just copy diskio and tweak everything) + documentation
 - get f_seek_w working like in the BASIC program  - this needs the changes to diskio.f_open to use suffixes ,p,m
 - attempt to fix the expression codegen bug with reused temp vars (github #89)
diff --git a/examples/cx16/pcmaudio/adpcm.p8 b/examples/cx16/pcmaudio/adpcm.p8
index 1917207d2..38ae5446a 100644
--- a/examples/cx16/pcmaudio/adpcm.p8
+++ b/examples/cx16/pcmaudio/adpcm.p8
@@ -3,6 +3,23 @@
 %option no_sysinit
 %zeropage basicsafe
 
+;
+; IMA ADPCM decoding and playback example.
+; https://wiki.multimedia.cx/index.php/IMA_ADPCM
+; https://wiki.multimedia.cx/index.php/Microsoft_IMA_ADPCM
+;
+; IMA ADPCM encodes two 16-bit PCM audio samples in 1 byte (1 word per nibble)
+; thus compressing the audio data by a factor of 4.
+; The encoding precision is about 13 bits per sample so it's a lossy compression scheme.
+;
+; NOTE:  this program requires 16 bits MONO audio, and 256 byte encoded block size!
+; HOW TO CREATE SUCH IMA-ADPCM ENCODED AUDIO? Use sox or ffmpeg:
+; $ sox --guard source.mp3 -r 8000 -c 1 -e ima-adpcm out.wav trim 01:27.50 00:09
+; $ ffmpeg -i source.mp3 -ss 00:01:27.50 -to 00:01:36.50  -ar 8000 -ac 1 -c:a adpcm_ima_wav -block_size 256 -map_metadata -1 -bitexact out.wav
+;
+; THEN use a tool to read the raw audio frame data from that resulting out.wav and save it as 'adpcm-mono.bin'.
+;
+
 main {
 
     ubyte num_adpcm_blocks
@@ -179,7 +196,7 @@ adpcm {
 
 
 audiodata {
-    ;; %option align_page
+    %option align_page
 adpcm_data:
     %asmbinary "adpcm-mono.bin"
 adpcm_data_end: